I. both¹ S1 W1 /bəʊθ $ boʊθ/ determiner, predeterminer, pronoun

1. used to talk about two people, things etc together, and emphasize that each is included ⇒ either:
Both Helen’s parents are doctors.
Hold it in both hands.
You can both swim, can’t you?
They both started speaking together.
Oxford is not far from Stratford, so you can easily visit both in a day.
both of
Both of my grandfathers are farmers.

2. somebody can’t have it both ways used to say that someone cannot have the advantages that come from two separate situations because they cannot exist together:
It’s either me or her. You can’t have it both ways.


GRAMMAR
Use both (of) before 'the', 'my', 'these' etc, or use both directly before a plural noun:
Both my parents are dead (NOT My both parents are dead).
Both of her parents went to college.
Both parents seem to be working very hard.
When both follows a pronoun or noun referring to two people or things, it should come after the first auxiliary if there is one:
We have both worked in Scotland for some time. It comes after a simple tense of 'be':
a subject in which you are both interested
► Both is not usually used in a negative clause. Use a clause with neither instead:
Neither of these methods is perfect (NOT Both of these methods is not perfect).

[TahlilGaran] Dictionary of Contemporary English ▲

II. both² conjunction
both ... and ... used to emphasize that something is true not just of one person, thing, or situation but also of another:
He’s lived in both Britain and America.
She can both speak and write Japanese.
Both he and his wife enjoy tennis.

[TahlilGaran] Dictionary of Contemporary English ▲

both
pronoun
1.
BAD: Both of them have not apologized yet.
GOOD: Neither of them has apologized yet.
BAD: Both the husband and the wife aren't reliable.
GOOD: Neither the husband nor the wife is reliable.

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2.
BAD: Anne and John both are scientists.
GOOD: Anne and John are both scientists.
BAD: Two of the biggest firms are Apple and IBM, which both are in the computer business.
GOOD: Two of the biggest firms are Apple and IBM, which are both in the computer business.

[TahlilGaran] Dictionary of Common Errors ▲

both
bəuθ
See: cut both ways , plague on both your houses

[TahlilGaran] English Idioms Dictionary ▲