Today's word is OLEUM, which is a second-declension neuter noun.
Latin meaning and usage: The word oleum means "oil," especially "olive oil." We are used to the importance of olive oil in the kitchen, but for the ancient Romans, oil was also an important part of the bath ritual and oil was also used to anoint the bodies of wrestlers - as if wrestling were not a difficult enough sport already! Recall also that oil was used for lamps in the ancient world.
Latin word formation: Compare the Latin word for oliva, olea.
English cognates and derivatives: Most obviously, we get the English word "oil" from this Latin word, but there are some other interesting words that come to us from Latin oleum. For example, there is English "linoleum," a compound of linum, "flax, linen" and oleum; originally, "linoleum" referred to a linseed oil preparation that was used to manufacture floor coatings, and only later did it come to refer to the actual floor covering material that we know today as "linoleum." In chemistry, the -ol suffix usually refers to alcohols, but it can also come oleum as most famously in "petroleum" or, in British English, "petrol." Compare also "lanolin," a word that is a combination of Latin lana, "wool" and the -ol suffix from oleum. So too "menthol," which is mint oil. The -ol in English "gasoline" also derives from oleum. You may also have heard the term "oleo" or "oleomargarine" in English, although now we usually just say "margarine."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:
Oleum in ignem.
Oleum camino addis.
Since I don't have many proverbs to offer, let me share this fable of Mercury and the dog, which involves oleum (fable source):
789. Mercurius et Canis. Stabat in via Mercurius quadrangularis, imus cui subiacebat lapidum acervus. Accedens canis “Primum, salve,” inquit, “Mercuri; tum inungere te volo, nec sic Deum praeterire eumque palaestritam.” Cui Deus, “Si mihi hocce, quod adpositum est, non linges oleum, nec imminxeris mihi, gratiam habebo tibi. Neque me amplius honorare velis.”