You hear both terms in DnB conversations and they sound like synonyms. They are not. They describe related but distinct production techniques. Mixing them up makes you look like you have not actually studied the records you are claiming to know.

Half-step

Within a 174 BPM DnB track, the snare pattern halves. Instead of hitting on beats 2 and 4, the snare only hits on beat 3. The bass and the hi-hats keep going at full DnB intensity. The track feels like it has dropped tempo without actually dropping tempo. Energy goes inward.

Halftime

An entire track at 85-90 BPM that uses DnB-style production values: heavy sub-bass, complex drum patterns, the same studio approach. Often produced by DnB producers as a side project or a EP B-side. The Critical Music halftime catalogue is the canonical example.

In a DJ context

Half-step plays as part of a DnB set. You drop into half-step for 15 minutes around the middle of your set, then come back to full DnB. Halftime plays as a separate set, usually slower, often at warm-up tempo or in a side-room context.

Why the distinction matters

If you are a DJ and you ask a promoter "do you want a halftime set", you are asking for a slower, separate set. If you mean "I will include half-step sections in my DnB set", say that. Promoters get confused by the conflation and the wrong set lands in the wrong slot.