The term "gi" is actually a suffix in the Japanese language denoting a form of clothing, rather than a standalone word. It features in words such as "Judogi" denoting a Judo uniform, and more generally "Keikogi" as a practice uniform.

It has become a shorthand outside of Japan for modern practitioners of martial arts to refer to practice uniforms specific to those martial arts. So a BJJ practitioner will talk about their "gi", when they mean a uniform specific to BJJ, whereas an Aikido or Karate practitioner referring to their "gi" would mean entirely different types of uniforms specific to their arts.

The BJJ gi is similar to a Judogi, in that it features a heavy, textured fabric with a sturdy, wide lapel, pants with reinforced knee patches, and a sturdy belt. The BJJ gi differs from a Judogi in that a Judogi features a baggier, longer jacket, whereas a BJJ gi has a slimmer, more form-fitting jacket and often lighter fabric weaves. Modern BJJ gis are often constructed to avoid the prominent back seam in Judogis (s(eparating the top half of the Judogi jacket from its skirt), as these can lead to abrasions when doing extensive ground fighting. BJJ gis also tend to feature more reinforcement of the pants due to the more extensive gripping of the legs and movement on the ground.

BJJ organizations often regulate the fabrics and dimensions of the BJJ gi in competition, but modern BJJ practice gis often stray from these competition cuts, for example by using ligher fabrics or different fabric weaves that don't significantly disrupt training.

Both BJJ gis and Judogis are constructed to withstand an extensive amount of gripping and tension, so will resist tearing even after years of training, whereas a normal shirt or jacket might tear instantly if gripped and pulled on.