Check in and Sit-down

Check in verb - Announce one's arrival, e.g. at hotels or airports.

Sit-down and check in are semantically related. In some cases you can replace phrase "Sit-down" with "Check in", this terms are similar.

Sit-down noun - A strike in which workers refuse to leave the workplace until a settlement is reached.

Check in and sit-down are semantically related. Sometimes you can use "Check in" instead a verb phrase "Sit-down".