Today's word is SUUS, which is a first-second declension adjective.
Latin meaning and usage: This is the reflexive possessive adjective, indicating that something belongs to the subject of the main verb of the sentence. As a result of referring back to the subject of the sentence, you will usually see this adjective in cases other than the nominative, but you can also see the nominative form referring to the logical subject of the sentence, as in this example: Suus est mos cuique genti, "To each people there is their own custom" = "Each people has their own custom." Note that suus is used for third-person forms (his, her, its, their) only; for first- and second-person forms, you have other possessive adjectives: meus, tuus, noster, vester.
Latin word formation: Just as with mei, tui, nostri and vestri, the genitive sui can be used to express an objective form, e.g. amor sui, "love of yourself." There are also emphatic forms of the pronoun formed with -met (e.g., suamet as an emphatic form of sua) and with -pte (e.g., suopte as an emphatic form of suo).
English cognates and derivatives: The Latin phrase sui generis is one that is freely used in written English. The ancient Romans did not use the word "suicide," but it is formed from Latin roots; compare the similar words "homicide," "patricide," etc. which you can find in Latin as homicida and patricida.
Here are some examples of today's word in Latin sayings and proverbs; for more examples, see the page at the Scala Sapientiae, which also contains notes on some of the proverbs cited below:
Omnis est rex in domo sua.
Suo quaeque tempore facienda.
Sibi quisque habeat quod suum est.
Sua tenenda cuique.
Omnes quae sua sunt, quaerunt.
Suus cuique mos.
Accipe quod tuum alterique da suum.
Alterius ne sit, qui suus esse potest.
Stat sua cuique dies.
Suus est mos cuique genti.
Sua cuique natura est ad vivendum dux.
Sibi habeat suam Fortunam.
Habet et bellum suas leges.
Sua quemque sequuntur fata.
Agunt opus suum fata.
Redde cuique quod suum est.
Multi ad fatum venere suum, dum fata timent.
Fortunam suam sibi quisque ipse parat.
Sua cuique hora.