if

If is a word used as a conjunction and subordinating connector to introduce conditional clauses. It marks a condition that must be met for a second event to occur or a hypothetical outcome to be true. In English, it is used across real, possible, and hypothetical situations, as in If it rains, we will stay indoors. Depending on the tense and form, English can express real, possible, or hypothetical conditions, including mixed and counterfactual forms such as If I had known, I would have acted differently.

In logic and mathematics, the conditional connective is expressed as an implication, often written as if p then q (p → q). A conditional statement asserts that whenever the first proposition (the antecedent) is true, the second proposition (the consequent) follows. The concept is central to formal reasoning, though natural language uses more nuanced forms that handle ambiguity, necessity, and counterfactuals.

In computer programming, the if statement provides conditional branching. It tests a boolean expression and executes a block of code if the condition is true; otherwise, it may execute an alternative block (else) or skip execution. Many programming languages support variations such as else if chains, nested conditionals, and conditional expressions.

In culture, the word If appears as a title for various works, including Rudyard Kipling’s poem If—, which discusses personal conduct and virtue, and several songs and literary pieces that explore themes of possibility, choice, and consequence.