/ bəʊθ; NAmE boʊθ/ determiner , pronoun
1.
used with plural nouns to mean 'the two' or 'the one as well as the other' :
Both women were French.
Both the women were French.
Both of the women were French.
I talked to the women. Both of them were French / They were both French.
I liked them both.
We were both tired.
Both of us were tired.
We have both seen the movie.
I have two sisters. Both of them live in London / They both live in London.
Both (my) sisters live in London.
2.
both ... and ... not only ... but also ... :
Both his mother and his father will be there.
For this job you will need a good knowledge of both Italian and Spanish.
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WORD ORIGIN
Middle English : from Old Norse báthir .