Regimen and cycles
A regimen is a named recipe of drugs, doses and timing; a cycle is one round of it, usually two to four weeks, giving normal tissues time to recover before the next. 'Six cycles of FOLFOX' means six repeats of that recipe.
Regimens are named by acronym (R-CHOP, FOLFOX, AC-T, VRd, 7+3) or trial (the KEYNOTE-522 regimen), specify each drug's dose per body surface area or weight and its schedule (day 1, days 1-14), and are given for a defined number of cycles or until progression or intolerance. Cycle length is set by marrow recovery, so dose-dense schedules need growth factor support. Modern regimens increasingly mix chemotherapy with antibodies and immunotherapy, and fixed-duration versus continuous designs are a live question in many diseases.