Where you put only changes the meaning (B2 Grammar)
The word only limits whatever comes right after it. Move only, and you change which part of the sentence it points to. Put it next to the word you mean.
only sits next to what it limits
Only Amina saw him. (nobody else saw him)
Amina only saw him. (she saw him, but didn't speak to him)
Amina saw only him. (she saw him and no one else)
Not "Only I saw him yesterday. (do you mean only me, or only yesterday?)" — say "I saw him only yesterday. (not before then)". Put only right before the exact word you want to limit.
Try it: A whole group was in the room, but out of all of them, just one person, Diego, noticed the message. Nobody else did. Which one says nobody else noticed it? (Only Diego noticed the message. / Diego only noticed the message.) Answer: Only Diego noticed the message. — To say nobody else noticed, only goes right before Diego: Only Diego noticed. Putting only before "noticed" would instead mean he noticed it but did nothing more about it, which isn't the point here.
only before the thing or the time
Slide only further along and it limits the thing or the time instead. Same word, different spot, different meaning.
She trusts only him. (no one else, just him)
We met only once. (one time, not more)
I found out only yesterday. (not before then)
Try it: Sofia has many colleagues, but there is one single person she would share the secret with, and absolutely no one else: Mateo. Which one says she'd tell that one person and nobody else? (Sofia would tell only Mateo. / Only Sofia would tell Mateo.) Answer: Sofia would tell only Mateo. — The one person she'd tell is the point, so only goes before Mateo: tell only Mateo. "Only Sofia would tell Mateo" changes the meaning to nobody but Sofia would do the telling, which is about the wrong part.
only before a time word
Put only right before a time word and it limits when — it means "not before then" or "no more than that". The time is the part you're narrowing down.
I heard only this morning. (not before then — the news is fresh)
We met only once. (one time, no more)
The shop opens only on Sundays. (no other day)
Not "Only I heard this morning. (this sounds like nobody else heard it)" — say "I heard only this morning. (I'm stressing how recent the news is)". Drop only right next to the time word when the when is your point.
Try it: The point is that just one person, and no one else, passed the test: Wei. The point is how recent it was: the news reached them as late as this morning, not before. Match each one. Where does only go? Answer: The point is that just one person, and no one else, passed the test: Wei. → 1 → Only Wei passed the test. · 2 → They heard only this morning. The point is how recent it was: the news reached them as late as this morning, not before. → 1 → Wei passed only the test. · 2 → Only they heard this morning. — To say nobody else passed, only goes before the person: Only Wei passed. To stress how recent it was, only goes before the time: only this morning. "Wei passed only the test" is correct English too, but it means he passed nothing besides the test — a different point. The spot you put only in decides which part it limits.
Loose in speech, precise in writing
In everyday speech, people usually just drop only in front of the verb — "I only saw him yesterday" — and let tone of voice and context sort out which part they mean. In careful writing there's no voice to guide the reader, so you move only right next to the exact word it limits. This precision matters most in formal writing: reports, instructions, contracts, notices.
Spoken, relaxed: "I only saw him yesterday." (could mean just him, or just saw and didn't speak, or just yesterday — the listener works it out)
Written, precise: "I saw only him yesterday." (him and nobody else)
Written, precise: "I saw him only yesterday." (as recently as yesterday, not before)
Not "The offer only applies to new members. (fine when spoken; leaves room to misread on paper)" — say "The offer applies only to new members. (unmistakable in writing — no one else qualifies)". Pre-verb only is natural in speech; in formal writing, place only next to the word it limits.
Try it: You're drafting a formal notice. You need it to be unmistakable that the discount is for members and nobody else. The reader has no tone of voice to guide them. Which one is clearer in careful writing? (The discount applies only to members. / The discount only applies to members.) Answer: The discount applies only to members. — Said out loud, both sound the same and nobody would misread them — everyday speech just parks only before the verb. But careful writing has no tone to lean on, so put only right before the words it limits: only to members. Only applies before the verb is common when speaking, yet on paper it leaves the sentence looser than a formal notice wants.