“Brainstorm” once referred to a violent mental disturbance. Today it usually means a fast, creative session for generating ideas.

British English usually prefers at the weekend, while American English usually prefers on the weekend. Both mean the same thing.

Blatant means obvious and often shameless. Flagrant means glaringly bad or clearly against rules, standards, or basic decency.

British English often says leftenant, while American English says loo tenant. The difference comes from older French influenced history.