Roe

Salmon roe at the Shiogama seafood market in Japan

Roe is the fully ripe egg masses of fish and certain marine invertebrates, such as sea urchins.

As a seafood it is used both as a cooked ingredient in many dishes and as a raw ingredient.

A variety of roe types is used in Japanese cuisine, including the following which are used raw in sushi:

Ikura - Salmon roe. Large reddish-orange individual spheres. Since salmon eggs are also used as bait, first-time sushi eaters who have experience fishing may be intimidated.
Kazunoko - Herring roe, pinkish yellow, usually pickled. The roe is in a single cohesive mass and so looks like a piece of fish.
Masago - small eggs of the Capelin, slightly orange in color
Tobiko - Flying-fish roe, very crunchy. Similar in appearance to Masago, but more red.
Uni - sea urchin roe, soft and melting. Color is an indication of quality and can range from orange to pale yellow.

Lumpfish (stenbider) roe is used extensively in Danish cuisine, on top of halved or slicd hard-boiled eggs, on top of mounds of shrimp, or in combination with other fish or seafood. Another commonly eaten roe is that from the cod (torsk).

Taramosalata is a well-known Greek dish consisting of roe pureed with some boiled potatoes.

Caviar is the name for sturgeon roe consumed as a delicacy.

ROE is also a military acronym meaning "Rules of Engagement."