Why this matters: a lot of great crochet magazines and patterns — Simply Crochet among them — are written in UK terms. UK and US crochet use the same stitches but swap the names almost entirely, so following a UK pattern with US terms in your head will not turn out right.

Stitches

These are exact, 1-for-1 swaps — same stitch, different name.

UK termUS term
Double crochet (dc) Single crochet (sc)
Half treble crochet (htr) Half double crochet (hdc)
Treble crochet (tr) Double crochet (dc)
Double treble crochet (dtr) Treble crochet (tr)
Triple treble crochet (trtr) Double treble crochet (dtr)
Slip stitch (ss) Slip stitch (sl st) same stitch
Chain (ch) Chain (ch) same stitch

Other pattern words

Not stitches, but common enough to trip you up mid-row.

UK termUS term
MissSkip
TensionGauge
Yarn over hook (yoh) Yarn over (yo)