ob-4 +

(Latin: down)

Before c, ob- becomes oc-; before f, ob- becomes of-; before g, ob- becomes og-; before p, ob- becomes op-; before m, ob- becomes o-

occasion (s) (noun), occasions (pl)
1. A particular time, especially as marked by certain circumstances or occurrences: Tim and Rene met on three occasions to discuss the project.
2. A special or important time, event, ceremony, celebration, etc.: Hank's birthday will be quite an occasion.

Henry was filled with both joy and fear on the occasion of his wedding.

3. A convenient or favorable time, opportunity, or juncture: This slack period in business would be a good occasion to take an inventory.
4. The immediate or incidental cause or reason for some action or result: Jack asked, "What is the occasion for all of this noise?"