statim

statim is built on sto, "to stand", and originally meant "standing where you are", on the spot. That is still the force of it: not soon, but now, with no gap. Its neighbour mox is "soon, shortly" and does allow a gap, so the two are not interchangeable.

With ut or atque following, it turns into a conjunction: statim ut hoc audivit, "the moment he heard this". Worth knowing that this word ranks far higher in our corpus than it would in Caesar alone, because the Vulgate leans on it constantly, especially Mark's gospel, which uses statim to render the Greek narrative tic "euthys". In classical prose it is common but not relentless.