A stipulation is the condition itself — the particular thing that an agreement, a law or a rule says must happen. If a contract stipulates something, that something is a stipulation. It is a countable noun, so you can have one stipulation or several: 'the loan came with two stipulations'. The word carries the sense of a string attached: the deal is available, but only if this is true. Very often it appears in the pattern 'with the stipulation that…' or 'on one stipulation' — 'he gave them the house, with the stipulation that they never sell it.' It can also mean the act of stipulating, though that use is rarer and quite formal. Like the verb, it belongs to written and official English: contracts, wills, grant conditions, rules of a competition. In everyday speech people say 'condition', 'a catch', or 'one thing though' instead. In American courtrooms it has the extra legal sense of a point both sides have agreed to accept, so that it does not need to be proved — you may see 'the parties filed a stipulation'.