Collar Length
The shortest classic length, around 12 to 13 inches, worn tight against the middle of the neck.
A collar sits above where a choker sits, usually in multiple rows, wrapping the neck itself.
It is a strongly formal, distinctly vintage look and demands an open neckline.
Most collars are multi-row, since a single strand at that length reads as insubstantial.
When you are buying
Collars are unforgiving on fit. Buy adjustable, or buy measured, and treat anything that sits tight without an extension as a made-to-measure purchase.
Choker Length
A necklace of about 14 to 16 inches, sitting snugly at the base of the throat.
Lines
How many parallel strands a necklace is made from. A 3-line necklace has three rows running together into one clasp.
Adjustable
A necklace or bracelet with an extension chain, letting the wearer add an inch or two.