SOBITA, konstanta, buzurgii doimiest dar tadqiqi matematiki, fiziki va khimiyavi. Buzurgii doimi dar rafti yagon prosess tagyir nameyobad. Sobit budani x-ro ba vositai alomati ramzi in tavr menavisand: kh = sonst.
Cobitaro beshtar bo harfhoi S, K va k ishorat mekunand.