The dot above an �i or �j' and the cross on a �t' may be called either a �jot' or a �tittle'.
A jot - from the Greek letter �iota' = �i' - means the least part of any writing. It can be applied to dots, strokes, Spanish tildes etc. A tittle is defined as a small stroke or point in writing. The two words are, effectively, synonyms, even though they are usually now combined in the phrase "not a jot or tittle".
There is a tendency to suppose that the jot is somehow tied to the dot, because a dot is what the letter �i' has and they share the �i' sound via the original word �iota'. By the same token, the tittle is often supposed to relate to the stroke on the �t', presumably because they share a �t' sound. However, either can be used for the i/j-dot or the t-stroke, really, or any other such mark.