US and UK crochet terms: the same word, two different stitches

When the pattern is in US terms

Term	In a US pattern it is	A UK pattern calls that
chain	chain (ch)	the same stitch, under the same name
slip stitch	slip stitch (sl st)	the same stitch, under the same name
single crochet	single crochet (sc)	double crochet (dc)
half double crochet	half double crochet (hdc)	half treble (htr)
half treble	not a US name	it is the UK name for US half double crochet (hdc)
double crochet	double crochet (dc)	treble (tr)
treble	treble crochet (tr)	double treble (dtr)
triple crochet	treble crochet (tr): another US name for it	double treble (dtr)
double treble	double treble crochet (dtr)	triple treble (trtr)
triple treble	triple treble crochet (trtr), which is not the UK stitch of that name	one step taller than the UK triple treble: go by the pattern's own stitch key
gauge	how many stitches and rows fit a measure	tension
tension	the UK word for gauge	it is the UK word for US gauge
yarn over	yarn over (yo)	the same action; also worded yarn over hook (yoh)
yarn over hook	yarn over hook (yoh): another wording of yarn over (yo)	the same action

This site uses US terms and gives the UK term beside the first use.
Triple treble is a name in both systems, for two different stitches: a UK triple treble is a US double treble crochet (dtr), and a US triple treble crochet (trtr) is a different, taller stitch. UK patterns shorten their triple treble trtr or ttr.
Yarn over (yo) and yarn over hook (yoh) are two wordings of one action, and patterns in US terms use both.

Term	In a UK pattern it is	A US pattern calls that
chain	chain (ch)	the same stitch, under the same name
slip stitch	slip stitch (ss)	the same stitch, under the same name
single crochet	not a UK name today; in old UK patterns it can mean a slip stitch (ss)	it is the US name for UK double crochet (dc)
half double crochet	not a UK name	it is the US name for UK half treble (htr)
half treble	half treble (htr)	half double crochet (hdc)
double crochet	double crochet (dc)	single crochet (sc)
treble	treble (tr)	double crochet (dc)
triple crochet	not a UK name	it is another US name for UK double treble (dtr)
double treble	double treble (dtr)	treble crochet (tr)
triple treble	triple treble (trtr)	double treble crochet (dtr)
gauge	the US word for tension	it is the US word for UK tension
tension	how many stitches and rows fit a measure	gauge
yarn over	yarn over (yo): another wording of yarn over hook (yoh)	the same action
yarn over hook	yarn over hook (yoh)	the same action; also worded yarn over (yo)

For the same stitch, the UK name is the US name one step up: a US single crochet is a UK double crochet, and a US double crochet is a UK treble.

Look for single crochet (sc) or half double crochet (hdc) anywhere in the pattern. UK terms as written today have neither name, so a pattern that uses one is written in US terms. The exception is an old UK pattern, where single crochet (sc) can mean a slip stitch.
Look for half treble (htr) as well. That name exists only in UK terms, so a pattern that uses it is written in UK terms.
If none of sc, hdc or htr appears, you cannot tell from the stitches alone: double crochet and treble are names in both systems. Look for a line that says which terms the pattern uses.
A pattern that speaks of tension is more likely to be in UK terms, and one that speaks of gauge in US terms. Take that as a hint, not as proof.

What is a UK double crochet in US terms?: A single crochet (sc).
What is double treble crochet in US terms?: A UK double treble (dtr) is a US treble crochet (tr). A US double treble crochet (dtr) is a UK triple treble (trtr).
What is a half treble?: The UK name for a half double crochet (hdc).
Is triple crochet the same as treble crochet?: Yes. Triple crochet is another US name for treble crochet (tr), which a UK pattern calls double treble (dtr).

Why do US and UK patterns use the same names for different stitches?: There are two systems of stitch names. Each uses the same few words, but the UK names start one step later, so every UK name stands for the stitch a US pattern calls by the name before it.
Are chain and slip stitch the same in both?: Yes. Chain is ch in both, and a slip stitch is the same stitch, shortened to sl st in US patterns and ss in UK ones.
Which countries use which terms?: US terms are used in the United States and Canada. UK terms are used in the United Kingdom and, among other places, Australia.

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