conj

• Supposing that, assuming that, in the circumstances that; used to introduce a condition that may be (or prove to be) either true or false.
  "if A then B else C"
• Supposing that; used with past or past perfect subjunctive to indicate a counterfactual or hypothetical condition.
  "I wouldn't marry you if you were the last man on earth."
• (sometimes proscribed) Whether; used to introduce a noun clause, an indirect question, that functions as the direct object of certain verbs.
  "I don't know if I want to go or not."

noun

• (informal) An uncertainty, possibility, condition, doubt etc.
  "The board can't approve this project; there are too many ifs."

noun

• (biochemistry) Initialism of intermediate filament.
• (electronics) Initialism of intermediate frequency.
• (nutrition) Initialism of intermittent fasting.