DEMi: abbreviation of demi-permanent

adjective  semi·per·ma·nent \-ˈpər-mə-nənt, -ˈpərm-nənt\

Demi-permanent color contains no ammonia and deposits only. It is mixed with a low-volume developer to help open the cuticle and lasts up to 24 shampoos. This type of color is great for blending gray, enhancing natural color, refreshing color, toning highlights, or for corrective work.