"Juventus stultorum magister" is a common Latin
aphorism, or phrase that has many implied and implicit meanings. The sentance translates to "youth is the teacher of fools
". One particular example of its use is in the movie Tombstone
. Johnny Ringo
uses it as a threat to Doc Holliday
during their famous Latin Converstaion
Juventus isn't really a latin word, they didn't use the letter 'J' so it is really Iuventus, which is in the nominative case (subject of the sentence), and it means youth or adolescence.
Stultorum is a latin derivation of the word stultus, stulti which means fool. The "orum" ending places it in the genative case, used (most frequently) to show possesion. Hence of fools.
Magister literally means teacher or schoolmaster. It is in the Nominative case as well.
There is an implied transitive verb such as "is" which would require the nominative case on both sides of the verb. Hence we have: "Youth is the teacher of fools".
It may be worthwhile to note that latin word order does not matter much, they use their nearly fully inflected language to specify subject, direct object, etc.