than

from The American Heritage® Dictionary of the English Language, 5th Edition.

• conjunction Used after a comparative adjective or adverb to introduce the second element or clause of an unequal comparison.
• conjunction Used to introduce the second element after certain words indicating difference.
• conjunction When. Used especially after hardly and scarcely:
• preposition In comparison or contrast with.

from The Century Dictionary.

• At that time; then. See then.
• A particle used after comparatives, and certain words which express comparison or diversity, such as more, better, other, otherwise, rather, else, etc., and introducing the second member of a comparison.
• Sometimes the preceding comparative is left to be inferred from the context; sometimes it is omitted from mere carelessness. A noun or a pronoun after than has a show of analogy with one governed by a preposition, and is sometimes blunderingly put in the objective case even when properly of subjective value: as, none knew better than him. Even Milton says than whom, and this is more usual: for example, than whom there is none better.

from the GNU version of the Collaborative International Dictionary of English.

• adverb obsolete Then. See then.
• conjunction A particle expressing comparison, used after certain adjectives and adverbs which express comparison or diversity, as more, better, other, otherwise, and the like. It is usually followed by the object compared in the nominative case. Sometimes, however, the object compared is placed in the objective case, and than is then considered by some grammarians as a preposition. Sometimes the object is expressed in a sentence, usually introduced by that.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• conjunction obsolete, archaic or dialectal (usually used with for) Because; for.
• conjunction Used in comparisons, to introduce the basis of comparison.
• preposition introduces 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.
• adverb At that time; then.