Today's word is OCULUS, which is a second-declension masculine noun.
Latin meaning and usage: The basic Latin meaning of the word is "eye," the organ of vision. In plants, the "eye" refers to a bud (we still use this sense in English, when we speak of the "eyes" of a potato, for example).
Latin word formation: The word oculus is cognate with the English word "eye" (the relationship is a bit easier to see, so to speak, if you consider the German word for eye, Auge). Although this is a very important noun in Latin, the root itself is not very productive; there are only a few words in Latin derived from this noun, such as the adjective ocularis.
English cognates and derivatives: We get the English "ocular" and "oculist" from this root, along with "binoculars" and "monocles." The English word "inoculate" is also from this root, and it originally meant to implant a tiny bud (in-ocul-) into a plant. With the word "daisy" (dæges eage "day's eye") we are using a similar metaphor as in the Latin name for this flower: solis oculus.
Here are some examples of today's word in Latin sayings and proverbs; for more information, see the page at the Scala Sapientiae, which also contains notes on some of the proverbs cited below, as well as additional proverbs:
Omnia videt oculus domini.
Oculus videns alia, seipsum non videt.
Plus vident oculi quam oculus.
Ubi amor, ibi oculus.
Magis vident oculi quam oculus.
Plus valent oculi quam oculus.
Oculi sunt in amore duces.
Anima pro anima, oculus pro oculo.
Sol oculus mundi.
Nemo videt oculum suum.
Amor ut lacrima oculo oritur, in pectus cadit.
Plura oculi quam oculus cernunt.
Procul ab oculis, procul a corde.
Quod procul ab oculis, procul ab animo.
Procul ex oculis, procul a corde.
Tam procul ex oculis, quam procul ex corde.
Oculos habentes non videtis et aures habentes non auditis.
Oculis magis quam auribus credendum est.
Oculis credendum potius quam auribus.
Oculis magis habenda fides quam auribus.