(colloquial) Nervous; worried.

A restrained or subdued situation. / (photography) A dark area of a photograph with little contrast.

(informal) Alternative spelling of low-key

(databases) A column (or group of columns) in a relational table that identifies another table, so that items in the two tables can be conceptually linked.

The unpublished key in asymmetric cryptography.

(computing, databases) In the design of a database table, the primary key (abbreviated PK) is selected among the non-empty set of candidate keys. The PK is a column (or an irreducible group of columns) able to identify every row of the table.

(electronics) A button, located along a display device, which performs whatever function is shown near it on the display.

(film, of lighting) Gently highlighting; low-key.

A can opener having a triangular tip that pierces the can. / Used other than figuratively or idiomatically: see church, key.

Alternative spelling of latchkey