Slot — Fourteen symbols; the unit the scheduler works in
The grid and its units
Where it sits
What it is
A slot is fourteen OFDM symbols with a normal cyclic prefix, twelve with an extended one. It is the unit the scheduler works in.
A slot is not a fixed duration — fourteen symbols of a numerology, so it halves as the numerology rises: 1 ms at 15 kHz, 500 µs at 30 kHz, down to 15.6 µs at 960 kHz. This is the single most useful fact about numerology: choosing a subcarrier spacing is choosing a scheduling interval.
A transmission need not fill one. PDSCH mapping type B starts at almost any symbol and may last as few as two, which is what makes low latency possible.
Read on
The full treatment is in nr-frame-structure — this page is the definition and the map reference; that note is where the subject is actually developed.
Before this concept, the hierarchy says to learn the following — the full chain, in order: