How do you say straight in French?

straight:

- as in a straight line... you would say... 'droite'

- as in straight hair... you would say ... 'raide'

- as in heterosexual.... you would say ...'hétérosexuel' or 'hétéro' for short

- as in straight ahead...you would say...'tout droit devant'

depends on the context
[go on] straight [ahead] (like a route description) = [continuez] droit [devant]

I have straight hair: j'ai les cheveux raides
first left, then straight: d'abord à droite, ensuite tout droit

straight/ straightforward: direct

straight (sexual orientation)= hétéro, hétérosexuel