sine qua non

1. A prerequisite (synset 105901868)
   is a type of: prerequisite, requirement - something that is required in advance
   same as: essential condition

Other Searches

• Rhyme: Dillfrog, RhymeZone
• Definition: Wiktionary, Dictionary.com, Wikipedia, Merriam-Webster, WordNet, Power Thesaurus
• Imagery: Google, Flickr, Bing