Pecten avi tandem sub pulvino inventus est.

The main clue is inventus est.

• inventus is a masculine singular nominative participle
• est means is here, but together inventus est makes a perfect passive verb: was found
• So the subject must be a masculine singular nominative noun

Pecten fits that perfectly, so it is the subject.

A beginner might expect a subject to come first and look very obvious, but in Latin the form of the words matters more than the order.

Because pecten is masculine.

The participle inventus must agree with the noun it goes with in:

• gender
• number
• case

Since pecten is masculine singular nominative, the participle must also be masculine singular nominative: inventus.

If the subject were neuter, then you would get inventum est instead.

Grammatically, it is a two-word verb phrase.

It is the perfect passive, made from:

• the perfect passive participle: inventus = found
• the present of sum: est = is

Together they mean was found.

So although it looks like found is, in normal English we translate the whole thing as a single passive verb idea: was found.

Here avi is best understood as the genitive singular of avus, meaning of the grandfather or grandfather’s.

So pecten avi means the grandfather’s comb.

This is a very common Latin pattern:

• noun + genitive
• pecten avi = comb of the grandfather

Yes, in isolation it could.

A learner might notice that avi could look like another form, especially if they know avis meaning bird. But in this sentence, the meaning and context point to avus.

So here:

• avi = of the grandfather
• not to the bird

This is normal in Latin: some forms are ambiguous until the rest of the sentence makes the meaning clear.

Because sub takes different cases depending on the meaning.

• sub
  • ablative = location, under
• sub
  • accusative = motion toward a position under something

Here the comb is already located there when it is found, so Latin uses the ablative:

• sub pulvino = under the pillow

If the idea were movement, such as he put it under the pillow, Latin could use the accusative instead.

Tandem means something like finally, at last, or after all this time.

Its position is flexible. Latin often places adverbs where they sound natural or where the writer wants emphasis. Putting tandem in the middle does not change the basic meaning.

So the sentence could be understood as:

• the grandfather’s comb was finally found under the pillow

Latin word order is much freer than English word order.

Because Latin relies much more on endings than on position.

English depends heavily on word order:

• The boy sees the dog
• The dog sees the boy

Those mean different things because the order changes.

Latin, however, marks a word’s job by its form. So even if the words move around, the endings still show what each word is doing.

In this sentence:

• pecten is the subject
• avi depends on pecten
• sub pulvino tells where
• inventus est is the verb

A more English-like order would be something like:

• Pecten avi sub pulvino tandem inventus est
• or even Tandem pecten avi sub pulvino inventus est

But the original order is perfectly normal Latin.

Because Latin has no articles.

Latin does not have separate words for:

• the
• a
• an

So pecten can mean:

• a comb
• the comb

Which one you use in English depends on the context and the intended meaning.

Because Latin genitives are often placed after the noun they modify.

So both of these are normal kinds of Latin order:

• pecten avi
• avi pecten

The first is especially common and natural in prose. English usually puts the possessive first, but Latin does not have to.

Yes, it is a third-declension noun, and that is why it looks less familiar.

Its dictionary form is:

• pecten, pectinis masculine

So:

• nominative singular: pecten
• accusative singular: pectinem

A learner might be surprised because pecten ends in -en, but that does not make it neuter. Its gender is masculine, which is why the sentence has inventus.