1. Without variation or change, in every case
   "constantly kind and gracious"
   - invariably, always 
2. Without interruption
   "the world is constantly changing"
   - always, forever, perpetually, incessantly, unremittingly

See also: constant

• preposition
• prepositional
• prepositional object
• prepositional phrase
• prepositionally
• prepositive
• prepossess
• prepossessing
• prepossession
• preposterous
• preposterously
• prepotency
• prepotent
• preppie
• preppy
• preprandial
• preprint
• prepubertal
• prepuberty
• prepubescent
• prepuce
• prepupal
• preputial
• prepyloric vein
• prequel