The date is not fixed on a calendar; it is counted from Easter, seven Sundays later, so it moves each year. The day looks back at one scene in the book of Acts, which is why services often use several languages. In Britain the same day is also called Whitsun or Whit Sunday, and this sense is British English. The word takes a capital letter and usually follows on or at.

This is the older of the two festivals the word names, and the Christian one is dated from it. Older English writing also calls it the feast of weeks. Context tells you which festival a text means: Easter nearby points to the Christian day, while Passover, Shavuot or the harvest points to this one.