The meanings will vary from organisation to organisation. In some cases the difference between "vice" and "deputy" isn't that great. For example in a school a vice principal and a deputy principal are roughly the same thing; one person who is second in charge of the school and who fills in for the principal in his or her absence. However if you look at an American company, for example, there will usually be many "vice presidents" who are responsible for specific areas of the company's operations (operations, human resources, finance, etc). Obviously not all of them are the "deputy" chief executive officer. Conversely in the navy there is a rank of Vice Admiral, the equivalent of a three star general. They may be completely in command of a fleet. They are not necessarily second in command of anything. (They will have a commander who may be responsible for the whole theatre of operations, but they aren't his "deputy".) An assistant *may* be second in charge of something, or they may not be in charge of anything at all; for example an executive assistant will organise an executive's calendars, travel, meetings and so on but does not step into his or her shoes while they are away. Sub also depends on context. For example sub-editors in a newspaper (the ones who are left) are not deputies to the editor but rather people who have the function of editing the text of the writers. Associate is even less likely to be similar to a deputy. For example in a court you will normally have a chief justice and several associate justices. They aren't the chief justice's deputy and they don't all have the same "rank"; the most senior will normally become acting chief justice when necessary. In short, they do not all mean the same thing and their meaning will depend entirely on the context of the organisation that uses those titles.