Body language was a range of non-verbal communication signals that an Individual could use to communicate their feelings and intentions.
In 2364, Deanna Troi said, "From Karnas' body language as well as his words and tone, I'd judge that what Karnas said was honest." (TNG: "Too Short A Season")
In 2259, Lt. Erica Ortegas surmised that Lt. Spock and Admiral Pasalk were having a pleasant conversation regarding Lieutenant commander Una Chin-Riley's trial. However, Doctor Joseph M'Benga pointed out that, based on the pair's body language, they actually hated each other. (SNW: "Ad Astra per Aspera")