A clear guide By which or in which

Many people ask which phrase to use. This guide explains what each phrase means. It gives easy examples for better understanding. Short sentences are used to name the parts of speech.

We will check verbs and make sure they match the subject. We will fix common mistakes. After reading, you will feel sure which phrase to choose.

Table of Contents

Parts-of-speech analysis of the introduction (every word tagged, tense and agreement checked)

I will mark each word with its part of speech. I will also say if the verbs use the right tense and match their subjects.

This article is about by which or in which

This — pronoun (points to the article)
article — noun (thing)
is — verb, present simple; subject This article is singular → is correct.
about — preposition (shows topic)
by — preposition (part of phrase by which)
which — relative pronoun (refers to thing)
or — conjunction (joins choices)
in — preposition (part of phrase in which)
which — relative pronoun
Sentence check: complete, not a fragment, not a run-on.

Many people ask which phrase to use

Many — determiner/adjective (describes people)
people — noun (plural)
ask — verb, present simple; plural subject people → ask correct.
which — pronoun (asks for choice)
phrase — noun
to — infinitive marker
use — verb (base form)
Sentence check: clear and complete.

We will show what each phrase means

We — pronoun (plural)
will show — future tense (auxiliary will + verb) — correct for we.
what — relative pronoun (introduces clause)
each — determiner/adjective
phrase — noun (singular)
means — verb, present simple; matches singular phrase — correct.
Sentence check: good.

We will give easy examples

We — pronoun
will give — future tense — correct.
easy — adjective (describes examples)
examples — noun (plural)
Sentence check: short and correct.

The parts of speech are explained using short sentences

We — pronoun
will name — future tense — correct.
the — article
parts — noun (plural)
of — preposition
speech — noun
in — preposition
short — adjective
sentences — noun (plural)
Sentence check: clear.

We will check verbs and make sure they match the subject

We — pronoun
will check — future tense — correct.
verbs — noun (plural)
and — conjunction
make sure — verb phrase (infinitive used with implied will)
they — pronoun (refers to verbs)
match — verb (base form) — used with make sure; acceptable.
the — article
subject — noun (singular)
Sentence check: grammatically fine.

We will fix common mistakes

We — pronoun
will fix — future tense — correct.
common — adjective
mistakes — noun (plural)

After reading, you will feel sure which phrase to choose

After — preposition (starts phrase)
reading — gerund (noun form of verb)
, — punctuation
you — pronoun
will feel — future tense — correct.
sure — adjective (describes you)
which — pronoun
phrase — noun
to choose — infinitive phrase (verb)
Sentence check: complete, good flow.

**Key point — what do by which and in which mean?**

We explain the meaning in plain words. Each line has a short example and a parts-of-speech check.

by which = how; by means of which
- Use by which to talk about a way or a method. It can also show who did something in formal writing.
- Example: The rule by which we play is simple.
  - The (article) rule (noun) by (preposition) which (relative pronoun) we (pronoun) play (verb) is (verb) simple (adjective).
  - Verb check: is matches singular subject The rule. play is present simple; subject we → play correct.
in which = inside which; during which; in the situation which
- Use in which for place, time, or context. It relates to something inside or within.
- Example: The room in which I sleep is small.
  - The (article) room (noun) in (preposition) which (relative pronoun) I (pronoun) sleep (verb) is (verb) small (adjective).
  - Verb check: is matches singular room. sleep matches singular I because I sleep is correct.

Short rule: by which = by way of / how. in which = inside or during.

How they work in sentences (simple relative clause guide)

Both phrases appear in relative clauses. A relative clause gives more information about a noun. Keep sentences short.

Structure with by which: noun + by which + clause
- This is the method by which we learn.
  - This (pronoun) is (verb) the (article) method (noun) by (preposition) which (relative pronoun) we (pronoun) learn (verb).
  - Verb check: is matches This. learn matches we.
Structure with in which: noun + in which + clause
- That is the time in which we met.
  - That (pronoun) is (verb) the (article) time (noun) in (preposition) which (relative pronoun) we (pronoun) met (verb, past).
  - Verb check: is matches That. met uses past tense — correct if the meeting is in past.

Note: You can often use shorter words in speech: the way we learn, the time we met. But by which and in which are useful in formal or clear writing.

Clear examples with POS tags and verb checks

I give many short examples. Each example is followed by parts-of-speech notes and verb checks. This keeps the article simple and safe for grade 1–2 reading.

**Examples for by which (method / means)**

The tool by which we cut is sharp.
- The (article) tool (noun) by (preposition) which (relative pronoun) we (pronoun) cut (verb) is (verb) sharp (adjective).
- is matches tool.
A rule by which you can play is here.
- A (article) rule (noun) by (preposition) which (relative pronoun) you (pronoun) can play (verb phrase) is (verb) here (adverb).
- is matches rule.
The way by which they found it was lucky.
- The (article) way (noun) by (preposition) which (relative pronoun) they (pronoun) found (verb, past) it (pronoun) was (verb, past) lucky (adjective).
- Past verbs match past events.

**Examples for in which (place / time / context)**

The box in which the toys are is big.
- The (article) box (noun) in (preposition) which (relative pronoun) the (article) toys (noun, plural) are (verb) is (verb) big (adjective).
- are matches toys. is matches box.
The day in which we came was cold.
- The (article) day (noun) in (preposition) which (relative pronoun) we (pronoun) came (verb, past) was (verb, past) cold (adjective).
- Past verbs match past time.
The story in which she lives is sad.
- The (article) story (noun) in (preposition) which (relative pronoun) she (pronoun) lives (verb) is (verb) sad (adjective).
- lives and is match subjects.

Simple swaps and when they change meaning

Sometimes you can swap by which or in which with other words. Use the swap to check your meaning.

Swap by which → how or the way that
- The way by which we learn → The way we learn or how we learn.
- POS check: the (article) way (noun) we (pronoun) learn (verb).
Swap in which → in which → when, where, or during which (depending on meaning)
- The year in which I was born → The year when I was born.
- POS check: year (noun) when (relative adverb) I (pronoun) was (verb) born (past participle).

Be careful: swaps must keep the meaning. by which cannot always be replaced by in which. Check the job of the phrase: way vs place/time.

Common mistakes and how to fix them

I list common errors. Each has a wrong sentence and a correct fix. I also show parts of speech and verb checks.

Using in which when you mean by which

Wrong: The method in which we measure is simple. (This makes it sound like the method is inside something.)
- The (article) method (noun) in (preposition) which (relative pronoun) we (pronoun) measure (verb) is (verb) simple (adjective).
- Verb check: is matches method — fine grammatically, but meaning is off.
Fix: The method by which we measure is simple.
- Now by which shows the method as the way we measure.

Using by which when you mean in which

Wrong: The room by which I sleep is small. (This is odd; by which sounds like method, not location.)
- The (article) room (noun) by (preposition) which (relative pronoun) I (pronoun) sleep (verb) is (verb) small (adjective).
Fix: The room in which I sleep is small.
- in which shows inside the room.

Dropping the relative pronoun and making confusion

Wrong: The rule which we follow by is simple. (awkward order)
- The (article) rule (noun) which (relative pronoun) we (pronoun) follow (verb) by (preposition) is (verb) simple (adjective).
Fix: The rule by which we follow is simple. or better The rule we follow is simple.
- POS and verb checks: is matches rule.

Tense mismatch (subject-verb agreement)

Wrong: The way by which she find it were strange.
- The (article) way (noun) by (preposition) which (relative pronoun) she (pronoun) find (verb) it (pronoun) were (verb) strange (adjective).
- Errors: find should be found (past) or finds (present). were should match way → was.
Fix: The way by which she found it was strange.
- Verb check: found (past) matches action; was matches singular way.

Rule: Always make the verb fit the subject and the tense.

American vs British English — any difference?

Both American and British English use by which and in which. The grammar is the same. The difference is small and mostly style.

Formal writing (both US and UK) uses by which and in which often.
- Example: The process by which we vote is fair. (formal)
- Example: The house in which they live is old. (formal)
In casual speech, people use simpler words: how, where, when.
- US: the way we vote or how we vote.
- UK: the way we vote or how we vote.
No major differences in rules. Use what sounds best. In formal text, keep by which and in which.

Idiomatic expressions and real-life uses

Here are some real-life uses. Each short example shows a clear meaning.

The law by which the city is run. — means the law that makes the city run (method/means).
- The (article) law (noun) by (preposition) which (relative pronoun) the (article) city (noun) is run (verb phrase) — note passive voice: is run.
- Verb check: passive is run matches city.
The week in which the show airs is busy. — means the show airs during that week.
- The (article) week (noun) in (preposition) which (relative pronoun) the (article) show (noun) airs (verb) is (verb) busy (adjective).
- Verb check: airs matches show. is matches week.
The system by which votes are counted. — method for counting.
- The (article) system (noun) by (preposition) which (relative pronoun) votes (noun, plural) are counted (passive verb phrase).
- Verb check: passive are counted matches votes.

Passive voice note: We use passive to show the action without naming the doer. It is fine in many examples.

Practical tips — quick ways to choose

Use these short tips. They are simple and easy to remember.

Ask: Is it a way or a place?
- If way or method → use by which.
  - The road by which we travel → the road by which we travel = the road we use.
- If place, time, or inside → use in which.
  - The room in which we sit = the room we sit inside.
Swap with short words to test meaning.
- by which → try how or the way that. If it fits, use by which.
- in which → try where or when. If it fits, use in which.
Use plain speech for simple text.
- The way we learn instead of the way by which we learn.
- The time we met instead of the time in which we met.
Check subject and verb.
- Find the main noun. Use a verb form that matches it. The box in which the toys are is heavy. (toys are; box is)
When in doubt, rewrite the clause.
- Make the sentence short. We use the rule. is okay.

Rewrite and polish for clarity (still very simple)

Now I rewrite key ideas to make them clear and smooth. Sentences stay short and easy.

By which = by way of; it shows how or by what means. Example: The plan by which we act is strong.
- POS check: The (article) plan (noun) by (preposition) which (relative pronoun) we (pronoun) act (verb) is (verb) strong (adjective).
In which = in / during / inside; it shows place or time. Example: The night in which it snowed was cold.
- POS check: The (article) night (noun) in (preposition) which (relative pronoun) it (pronoun) snowed (verb) was (verb) cold (adjective).
Use little words if you need to be simple: how, where, when. They often work well.

Exercises — short practice (with answers and POS checks)

Try these tasks. Each task has the correct answer and a POS and verb check.

Fill the blank: The rule ___ we learn is clear.
- Answer: by which or that or we → Best: The rule by which we learn is clear.
- POS: The (article) rule (noun) by (preposition) which (relative pronoun) we (pronoun) learn (verb) is (verb) clear (adjective).
Fix the sentence: The house by which I sleep is warm.
- Fix: The house in which I sleep is warm.
- POS: The house (noun) in which (prep + rel pronoun) I sleep (verb) is warm (verb + adj).
Choose: The day ___ we met was sunny. (when / by which)
- Best: when or in which. by which is wrong here.
- POS: The day (noun) when (rel adv) we (pron) met (verb) was (verb) sunny (adj).
Rewrite simply: The method by which we cut the wood is safe. → The way we cut the wood is safe.
- POS: The way (noun) we (pron) cut (verb) the wood (noun) is (verb) safe (adj).

Conclusion

Use by which for ways and means.
Use in which for places, times, or contexts.
Swap with how, where, or when to test meaning.
Keep subject and verb in the right tense and number.
If confused, make the sentence short and simple.

FAQs

Q: Can I use by which to mean how? A: Yes. By which often means how or the way that.
Q: Can I use in which for time? A: Yes. In which can mean during which or when.
Q: Is in which the same as where? A: Sometimes. Use in which for formal writing. Where is simpler.
Q: Is by which the same as where? A: No. By which shows method, not place.
Q: Can I say the way by which? A: Yes. But the way that or how is simpler.
Q: Do Americans use different rules than Brits? A: No. The rule is the same for both.
Q: Can I drop which and still be correct? A: Sometimes. The way we learn is fine. But by which may sound more formal.
Q: Is passive voice OK with these phrases? A: Yes. Passive can be fine: the system by which votes are counted.
Q: How do I check verb tense? A: Find the subject. Pick present or past. Make the verb match.
Q: What if I am not sure? A: Rewrite with simple words: use how, where, or when.