Today's word is ALIUS, one of the sneakier adjectival pronouns in Latin. It is important to note some of the irregularities in its declension, such as the neuter singular nominative and accusative aliud and the dative singular for all genders alii, plus the fact the the genitive singular is alterius, from a different Latin adjective, alter. You can see a complete declension at the Wiktionary. In general, alius is used to mean "the other, another" from among many, while alter usually refers to the other of just two.
The same root as in alius appears in the Latin adverbs alias and also in alibi, both of which have been adopted as English words. Latin alias means "in another time, in another place," and in English it has come to mean specifically "by another name." Latin alibi means "somewhere else, in another place," and in English it means the legal plea that you were elsewhere when some event took place, making you innocent of any direct involvement. You can also see the word alius in the Latin abbreviation used in English: et al., which stands for "and others" (et alii or et alia).
There are many idiomatic uses of the word alius in Latin. Combined with atque or ac, the word can mean "other than," as in this say, Alia dicis ac sentis, "You say one thing and think another." You can also see it used with quam or nisi to mean "other than," as in the phrase nihil aliud quam, "nothing other than..." The word alius is also frequently used in distributive clauses, where we would say "one... another..." in English, or "some... others..." in the plural. For example, consider this proverb Alius alio nequior, "One is more wicked than the other." Here is an example in the plural: Alia aliis placent, "Some people like some things, other people like other things" - although the Latin sure is more economical in that last example!
Here are some examples of today's word in Latin sayings and proverbs; for more information, see the page at the Scala Sapientiae, which contains notes on some of the proverbs cited below, as well as additional proverbs:Dis aliter visum.
Non sibi, sed aliis.
Alia dicunt, alia faciunt.
Aliud est velle, aliud posse.
Alii alio modo.
Bonus esse non potest aliis malus sibi.
Aliter cum aliis agendum.
Aliter enim cum alio agendum.
Tanti eris aliis, quanti tibi fueris.
Alii homines, alii mores.
Alia tempora, alii mores.
Artes aliis aliae.
Virtute - non aliter.
Fac aliis sicut tibi.
Oculus videns alia, seipsum non videt.
Aliud legunt pueri, aliud viri, aliud senes.
Aetas alia ex alia oritur.
Alia ex aliis mala oriuntur.
Aliis si licet, tibi non licet.
Alia aliis placent.