Learn English – Difference Between To, For, and Till

Till and Until mean the same thing, till however is the informal version, until is deemed formal. Your definition should read "not till", not "till not".

"You cannot leave until you finish your homework" or "you cannot leave till you finish your homework", both mean the same thing.

Until would generally be used at the beginning of a sentence e.g. Until you finish your homework, you cannot leave.

It is commonly assumed that till is an abbreviated form of until, till is in fact the earlier form. Apparently formed by the addition of Old Norse "und ‘as far as’ several hundred years after the date of the first records for till.

We can plan an audit. The audit can be planned by us. The audit can be planned by someone else. But we are not planned; we (or they) are the planners. We are not the thing that is planned. We can be ready for the audit that is planned for Friday.