2.prepositionIntroduces a comparison, and is associated with comparatives, and with words such as more, less, and fewer. Typically, it seeks to measure the force of an adjective or similar description between two predicates.
"A player than whom none is more skillful."
3.conjunctionUsed in comparisons, to introduce the basis of comparison.
"she's taller than I am; she found his advice more witty than helpful; we have less work today than we had yesterday; We had no choice than to return home"
4.conjunction(obsolete outside dialectal, usually used with for) Because; for.