an appointment fixed in advance: a set time, a sacred festival, the place where God arranged to meet His people, an agreed gathering or signal, or the fixed moment of the end
This word comes from a verb that means to fix or agree on something ahead of time, so at its heart it names whatever has been settled by appointment rather than left to chance. That single idea fans out in several directions depending on what is being appointed: a moment on the calendar, a recurring religious festival held at that moment, the spot where two parties arrange to meet, the gathering itself, an agreed signal, even the fixed hour when history reaches its end.
The senses shade into one another because Israel's life with God tied them together. A festival is simply an appointed time that has become a fixed sacred event. The place where God promised to meet His people is named by the very same word, and so is the moment He has set for judgment to fall. So a reader who finds "the time God set" in one verse, "the feast" in another, "the meeting place" in a third, and "the appointed end" in a fourth is looking at one concept turned in different directions, not separate words that happen to be spelled alike.
By far the most common phrase the Bible builds on this word is the name of the portable sanctuary in the wilderness, usually translated "tent of meeting." There the word carries its meeting sense: it is the appointed place where God and Israel come together, named from God's own promise, "there I will meet with you." Roughly two thirds of all its appearances belong to that one phrase.
The poets and prophets press the word's range deliberately. Lamentations grieves that God let both the meeting place and the festivals be forgotten in the same breath, and Daniel takes the bare idea of a fixed time and makes it the word for the appointed end of all things. The same word that names the tent where God met Moses names the hour He has set for the close of history.