There is an advert currently doing the TV rounds which talks about someone accessing an ‘alternate universe’.
This might suffice for America where it’s common currency, but those of us here who wish to guard the mother tongue should rise up, protest, run through the streets naked, set fire to things – or at least frown in a sternly disapproving when the advert is aired.
‘Alternate’ means by turns, switching back and forth between one thing an another. It doesn’t mean ‘alternative’. ‘Alternative’ means ‘alternative’. You and I might visit each other’s houses on alternate weeks, whereas if we visited alternative houses we would avoid our own and find somewhere else.
What the ad is meaning to refer to is an alternative universe – one other than our own, which might be one among many others.