mientras

Mientras is a Spanish conjunction used to indicate time and, in some contexts, contrast. It primarily means "during the time that" or "while" and is used to describe actions happening at the same time as another action or to set a time frame for a second clause. It can also introduce a condition in phrases such as "mientras no..." or "hazlo mientras puedas."

In terms of grammar, the verb in the clause introduced by mientras agrees with the speaker's view of reality. When the situation is presented as factual or habitual, the subordinate clause usually uses the indicative: "Ella escucha música mientras cocina." When the action is hypothetical, future, or contingent, the clause often takes the subjunctive: "Hazlo mientras puedas." "Mientras no llueva, iremos."

Mientras is also used to express contrast, particularly in "mientras que," meaning "whereas" or "while" in opposing clauses: "Yo estudio, mientras que él no estudia." A common fixed expression is "mientras tanto," meaning "in the meantime" or "meanwhile."

Regional usage and notes: the conjunction is widely used across Spanish-speaking regions, with minor stylistic differences. The exact etymology is debated, but "mientras" is a standard part of modern Spanish grammar. See also: mientras que, mientras tanto.