Puer stilum amat, sed eum saepe amittit.

Because stilum is the direct object of amat: it is the thing the boy loves.

The dictionary form is stilus (stylus, pen, writing tool). In this sentence, it has to be in the accusative singular, and for a regular second-declension masculine noun that gives -um:

• stilus = the stylus/pen
• stilum = the stylus/pen as a direct object

So:

• Puer stilum amat = The boy loves the pen/stylus

Because eum is the accusative singular masculine form of the pronoun, and it refers back to stilum, which is a masculine noun.

In Latin, a pronoun usually matches the noun it refers to in gender and number:

• stilum = masculine singular
• so it/him referring to stilum becomes eum

Also, eum is accusative because it is the direct object of amittit (loses).

So:

• sed eum saepe amittit = but he often loses it

Even though English says it, Latin still uses the grammatical gender of the noun.

Because id is neuter, but stilus is masculine.

Latin pronouns must agree with the noun they refer to in gender:

• masculine: eum
• feminine: eam
• neuter: id

Since stilus is masculine, Latin says eum, not id.

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

So:

• puer can mean boy, a boy, or the boy
• stilum can mean a pen/stylus or the pen/stylus

You figure out which is best from the context. In a simple sentence like this, English often translates it as the boy and the pen.

Puer is nominative singular, which is the case typically used for the subject.

We know it is the subject for two reasons:

1. Case ending: puer is nominative.
2. Verb ending: both amat and amittit are third-person singular, matching puer = the boy / he.

So puer is the one doing the actions:

• he loves
• he loses

They are both present active indicative, third-person singular.

That means:

• amat = he/she/it loves
• amittit = he/she/it loses

In this sentence, the subject is puer, so:

• amat = the boy loves
• amittit = the boy loses

These are ordinary present-tense statements.

Because they come from different verb groups (conjugations).

• amat comes from amare = to love
• amittit comes from amittere = to lose

Both are third-person singular present, but different conjugations form the present stem differently:

• amare → amat
• amittere → amittit

So the difference is normal and comes from the verb’s dictionary form, not from a difference in person or tense.

Latin word order is more flexible than English word order because the endings show what each word is doing.

English depends heavily on position:

• The boy loves the pen is different from The pen loves the boy

Latin can show the roles through case endings:

• puer = nominative subject
• stilum = accusative object

So Latin can say:

• Puer stilum amat
• Stilum puer amat
• Amat puer stilum

All can mean The boy loves the pen, though the emphasis may change.

The order in your sentence is very natural and clear.

Saepe means often and is an adverb, so it modifies the verb amittit.

Latin adverbs are fairly flexible in position, but placing saepe before the verb is very common:

• eum saepe amittit = he often loses it

This placement keeps the sentence easy to follow and gives saepe a natural emphasis.

Sed means but.

It connects the two parts of the sentence and shows a contrast:

• Puer stilum amat = The boy loves the pen
• sed eum saepe amittit = but he often loses it

So the idea is: he loves it, but there is a problem—he keeps losing it.

Not as naturally in this sentence.

Latin often leaves out subject pronouns because the verb ending already shows the subject:

• amat already means he/she/it loves
• amittit already means he/she/it loses

But eum is an object pronoun, and here it helps show exactly what he loses. Without it, the second clause would just mean:

• sed saepe amittit = but he often loses

That sounds incomplete unless the object is understood very strongly from context. So eum is helpful and expected here.

Grammatically, eum is the same form that can mean him or it, depending on what it refers to.

Here it refers to stilum, which is a thing, so in English we translate it as it:

• eum = it

If it referred to a male person, then English would translate it as him.

So the Latin form is the same, but the English translation depends on the meaning.

More exactly, stilus means a stylus, a pointed writing instrument used especially for writing on wax tablets. In beginner Latin, it is often translated as pen just to make the sentence feel more natural in English.

So depending on context:

• stilus = stylus
• or more loosely pen

Both help convey the basic meaning, but stylus is the more historically precise word.