Today's word is CAUSA, which is a first-declension feminine noun.
Latin meaning and usage: The basic meaning of the Latin word is a "cause" or a "reason" or "motive" for something. It can also refer to an "occasion" or "opportunity." In legal language, it refers to a "lawsuit." The word is often used in the ablative with an accompanying genitive to mean "on account of something" or "for the sake of something," as in the Latin phrase still sometimes used in English, honoris causa.
Latin word formation: There is a diminutive form of the noun, causula. The word causidicus refers to an "advocate" or "pleader." You can also see this root in words like accuso and excuso. For those of you who speak Italian, this is the origin of the ubiquitous Italian cosa.
English cognates and derivatives: We get a large number of English words from this Latin word, such as the nouns "cause" and "causation," and the adjective "causal." The words "accuse," "excuse," "recuse," etc. also have Latin causa as their origin.
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:
Omnia causa fiunt.
Nihil fit sine causa.
Nisi causas scimus, nihil scimus.
Malus est vocandus, qui sua est causa bonus.
Tunc scimus, cum causas cognoscimus.
Timendi causa est nescire.
Bellum pacis est causa.
Pauperis in causa non auris sit tibi clausa.
Aurum et opes, praecipuae bellorum causae.
Helenae causa Troia arsit.
Causa proxima, non remota, spectatur.
Bona causa nullum iudicem verebitur.
Benignus etiam causam dandi cogitat.
Occasio causa scelerum.
Negandi causa avaro numquam deficit.
Tum sapimus, cum causas cognoscimus.
Motus sine causa nullus est.
Avarus ipse miseriae causa est suae.
Tandem bona causa triumphat.