In what instances do you use the nominative for the word preceding "of the," in oppose to the genitive. For example, in some of my sentences, I have the nominative, like "Forma terrae in Sicilia plana non est." But other times, it is genitive "Curae puellarum parvae sunt." Are there any rules to help me remember when you use what like in the two examples above? Thank you!

You're confusing the feminine nominative plural ending -ae with the feminine genitive singular, which is also -ae (both for nouns/adjectives in the first declension).

In "Forma terrae..." Forma is nominative singular = shape or form, while terrae is genitive singular. That sentence means "The form of land in Sicily is not flat."

The second sentence means "The cares of the girls are insignificant."
*Curae = nominative plural
*puellarum = genitive plural
*parvae = nominitive plural to agree with the subject, curae; it means several things: small, little, insignificant, slight, unimportant...

My best advice is to memorize the declensions and notice which endings could be mistaken for another -- and make sure you know when a word is being used as a nominative (for the subject or for the predicate nominative) and when it's being used as a genitive. Almost always, the word order will indicate that to you ... unless you're reading poetry! In poetry, the writers take all kinds of liberties, including "messing up" normal word order.

This is pretty good:
http://en.wikipedia.org/wiki/Latin_grammar

When I say memorize, I mean it. Latin is mostly very logical, but it's also a language and will have its little quirks. Memorizing declensions, conjugations, vocabulary, etc., is your primary strategy.

My most successful way to memorize vocabulary was to take 3" x 5" index cards and cut them into fourths so you have strips about 3" x 1¼" -- put the English on one side and the Latin on the other. It works for any language!

are these correct.

I have to change the tense in the capitalized word and translate the sentence.

Error humanum est.this is the question

answers below
Errare humanum est.

To err is human

urbs Deleo non potuit

Urbbs delviam non potuit

the city was not destroyed

Errare humanum est.

To err is human.
This looks correct. Remember that "errare" can also mean to wander, roam; to make a mistake, etc.

urbs Deleo non potuit
Urbbs<~~?? delviam non potuit
the city was not destroyed
Not quite. The word "potuit" is a form of "possum, posse" - to be able. It needs to be completed by an infinitive. "Deleo" needs to be in one of the infinitive forms (depending on which tense you use) so that the translation reads "The city could not be destroyed."

is this correct:

urbs delenda non potuit

The city could not be destroyed.

Here's a helpful strategy to translate any Latin sentence:

1) Verb
2) Subject/Predicate
3) Accusative. (Direct Object)
4) Remaining cases., which I like to call, extra junk.

Ex. Curae puellarum parvae sunt.

1) Verb- Sunt...3rd person, plural, present tense, active

2) Subject- Since the verb is plural, look for a subject that either ends in ae, i, or a. Since curae ends in ae, which is nom., plu., it would be the subject. Also, parvae agrees with curae, so that's the predicate.

3) Direct Object- There is no d.o., so skip this step.

4) Remaining- puellarum is gen, plu, so it is of the girls.

***Basically, do these four steps and parse as you go along so you can write a complete translation.

***And always remember genitive never starts a true latin sentence.

When deciding whether to use the nominative or genitive case before "of the," you need to consider the grammatical function of the noun in the sentence.

1. Nominative Case: The nominative case is usually used when the noun is the subject of the sentence or a predicate noun, which renames or describes the subject. In your example sentence, "Forma terrae in Sicilia plana non est," "Forma" is the subject of the sentence. It describes the state of the earth and, therefore, takes the nominative case.

2. Genitive Case: The genitive case is used to show possession, relationship, or other forms of association. In your second example sentence, "Curae puellarum parvae sunt," "Curae" is indicating possession or association between "care" and "girls." Therefore, "Curae" is in the genitive case.

Remember, these rules are not uniquely tied to "of the" construction but rather apply in general to the use of nominative and genitive cases in Latin.

To determine which case to use, ask yourself these questions:
- Is the noun the subject of the sentence? If yes, use the nominative case.
- Does the noun indicate possession, relationship, or association? If yes, use the genitive case.

By analyzing the grammatical function and the meaning you want to convey, you can determine whether to use the nominative or genitive case before "of the" in your sentences.