Often used phrases and fixed expression can survive for decades or even centuries, and they usually have their sources in spoken, informal language. As flat adverb have their origins in the times before the 18th century and in informal language, it is not very surprising that many of the examples defined as "phrases" overlap with the examples in "flat adverbs".

Often used phrases:

- go crazy (adjective!)
- break loose (adjective!)
- break free (adjective!)
- to keep something safe (adjective!)
- play it safe
- take it slow
- it works fine
- it works great
- play it cool (The Beatles: Hey Jude) (one could also argue that the person is cool while playing their game, so that "cool" is an adjective)

Fixed expressions:

- come true (true is an adjective)
- stoop low
- to go easy on sth./ to go easy on somebody
- easy-going
- to hold true for sth.
- "I would steer far clear." ("to steer clear from sth." means "to avoid sth", and "far" is a flat adverb)
- to be paid current (a very specific phrase, apparently American English only)