Top grass radical (Kangxi #140 in its 3-stroke compressed form) - the indexing radical here. Originally
营 was written with
火 marking a campfire surrounded by tents; the modern
艹 top is a graphic substitute, not a true grass-meaning. Most
艹 chars (
花,
草,
茶) are botanical, but
营 is a semantic outlier you have to memorize.
