inconstant

/ɪnˈkɑnstənt/

Other forms: inconstantly

Anything that's inconstant changes all the time. Don’t give your heart to an inconstant friend because she might get distracted and drop it. The moon is inconstant, with all that waxing and waning, but we love it anyway.

You can't exactly count on things — or people — that are inconstant, since they vary or waver so much. Someone who's inconstant is fickle or even undependable. An inconstant friend might promise to come to your party and then fail to show up because she suddenly felt like going bowling instead. When the weather is inconstant, you don’t know what to wear. The Latin root is inconstantem, "changeable or capricious."

Definitions of inconstant

1. adjective

   likely to change frequently often without apparent or cogent reason; variable
   “inconstant affections”

   “"swear not by...the inconstant moon"- Shakespeare”

   synonyms:

   changeable, changeful

   such that alteration is possible; having a marked tendency to change

   false, untrue

   (used especially of persons) not dependable in devotion or affection; unfaithful

   fickle, volatile

   marked by erratic changeableness in affections or attachments

   unfaithful

   not true to duty or obligation or promises

   unstable

   lacking stability or fixity or firmness

   variable

   liable to or capable of change

   volatile

   evaporating readily at normal temperatures and pressures

   antonyms:

   constant

   steadfast in purpose or devotion or affection

   unchangeable

   not changeable or subject to change

   staunch, steadfast, unswerving

   firm and dependable especially in loyalty

   unfailing, unflagging

   unceasing

   faithful

   steadfast in affection or allegiance

   stable

   resistant to change of position or condition

   invariable

   not liable to or capable of change