Fenus nimis magnum est.

Because fenus is in the nominative singular, which is the case normally used for the subject of a sentence in Latin.

In Fenus nimis magnum est, the basic structure is:

• fenus = subject
• magnum = adjective describing the subject
• est = is

So the sentence is built like X is Y.

Because magnum has to agree with fenus.

Fenus is:

• singular
• nominative
• neuter

So the adjective must also be:

• singular
• nominative
• neuter

That gives magnum.

This is a very important Latin rule: adjectives agree with the nouns they describe in gender, number, and case.

In Latin, grammatical gender is not always the same as natural gender. A noun can be masculine, feminine, or neuter even if it refers to an abstract idea or a thing with no biological sex.

So fenus is simply a neuter noun because that is how the word is classified in Latin vocabulary.

Nimis is an adverb meaning too, too much, or excessively.

Here it modifies magnum, so it means:

• magnum = big, large, great
• nimis magnum = too big / too great

So nimis does not describe fenus directly as a noun; it strengthens the adjective.

Latin word order is much more flexible than English word order because the grammar is shown by word endings, not mainly by position.

So Fenus nimis magnum est is natural Latin, even though in English we normally say:

• The loan is too large
• The interest is too great

Placing est at the end is very common in Latin, especially in simple statements.

Yes. Because of Latin's flexible word order, you could rearrange the sentence without changing the basic meaning, for example:

• Fenus est nimis magnum
• Nimis magnum fenus est
• Magnum fenus nimis est would be less natural for the intended meaning, because nimis usually goes closely with the word it modifies.

Even when the meaning stays basically the same, different word orders can change emphasis.
For example, putting nimis earlier can emphasize the idea of excess.

Latin does not have articles like English the or a/an.

So fenus can mean, depending on context:

• a loan
• the loan
• interest
• the interest

The exact English translation depends on the situation, not on a separate Latin word.

Yes. In Latin, an adjective can be used with esse (to be) as a predicate adjective.

So:

• fenus = the subject
• magnum est = is large / is great

This works just like English The loan is large.

You do not need another noun such as thing or amount.

Fenus is a third-declension neuter noun.

A learner may notice that its nominative form ends in -us, which can look masculine at first, but it is actually neuter. Latin has some neuter nouns in the third declension with forms that do not look like the common second-declension neuter endings such as -um.

So this is a good reminder: do not guess gender only from the nominative ending.

Both spellings are found. Faenus is a common classical spelling, while fenus is also attested.

So if a learner has seen faenus elsewhere, that is not a different word in meaning here. It is just a spelling variation.

Yes. Magnus, magna, magnum can mean:

• big
• large
• great

In a sentence like this, English might translate it in different ways depending on context:

• The interest is too great
• The loan is too large
• The debt is too large

So even though the grammar is straightforward, the most natural English wording can vary.

Latin often uses an adjective such as magnus where English might choose a slightly different expression.

So nimis magnum is literally too big/too great, but in natural English we might say:

• too large
• too great
• excessive

That is normal. A Latin sentence does not always match the most idiomatic English wording word-for-word.