Homo sapiens mendacium spernit et veritatem amat.

The subject is homo sapiens.

We know this because both words are in the nominative singular, the case normally used for the subject:

• homo = nominative singular of homo, hominis
• sapiens = nominative singular agreeing with homo

So the sentence is about one human being / the wise human / Homo sapiens doing the two actions.

This is a very common beginner question.

Latin nouns are assigned to declensions by their genitive singular, not just by how the nominative looks.
So:

• homo = nominative singular
• hominis = genitive singular

Because the genitive is hominis, homo belongs to the third declension.

So even though -o often makes English-speaking learners think of second-declension words like servus or dominus, homo is different.

Because sapiens is a third-declension adjective (historically a present participle), not a first/second-declension adjective like bonus, bona, bonum.

Its dictionary form is:

• sapiens, sapientis

It means wise, sensible, or knowing. Here it agrees with homo in:

• case: nominative
• number: singular
• gender: masculine

So homo sapiens is grammatically just a noun plus an agreeing adjective.

It can be understood that way, but grammatically it does not have to be.

In ordinary Latin, homo sapiens can simply mean a wise human being or man as a rational being. In modern usage, of course, it is also the familiar scientific label Homo sapiens.

So in this sentence, the phrase works perfectly well as normal Latin grammar:

• homo = human being
• sapiens = wise / knowing

Mendacium is accusative singular because it is the direct object of spernit.

The verb spernit means despises, rejects, or scorns, and the thing being despised goes into the accusative case.

Also, mendacium is a second-declension neuter noun. For neuter nouns of this type:

• nominative singular = -um
• accusative singular = -um

So mendacium looks the same in nominative and accusative singular.

Because veritatem belongs to a different declension.

It is the accusative singular of:

• veritas, veritatis = truth

This is a third-declension feminine noun, and its accusative singular ends in -em:

• nominative: veritas
• accusative: veritatem

So both mendacium and veritatem are direct objects, but they take different accusative endings because they belong to different noun classes.

Both verbs are:

• third-person
• singular
• present
• active
• indicative

More specifically:

• spernit = from spernere, he/she/it despises
• amat = from amare, he/she/it loves

They are singular because the subject, homo sapiens, is singular.

Latin usually does not need a separate subject pronoun like he or it, because the verb ending already tells you the person and number.

Classical Latin has no articles like English the, a, or an.

So a noun like homo can mean, depending on context:

• a human
• the human
• humanity / man

The reader figures this out from context and meaning, not from a separate article word.

That is why the sentence can be translated naturally into English in more than one way.

Et means and.

Here it joins the two verbal ideas:

• mendacium spernit
• veritatem amat

Both actions share the same subject, homo sapiens.

So the structure is basically:

• Humanity despises falsehood and loves truth

Latin often leaves the subject unstated after the first verb if it is still the same subject, just as this sentence does.

The word order is not fixed in the way English word order usually is.

Because Latin uses case endings to show each word’s role, you could rearrange the sentence in several ways without changing the basic meaning, for example:

• Homo sapiens veritatem amat et mendacium spernit
• Mendacium homo sapiens spernit et veritatem amat
• Veritatem amat et mendacium spernit homo sapiens

The original order is fairly straightforward and easy to read. It has a natural rhythm:

• subject first
• object + verb
• object + verb

Changing the order would mainly change emphasis, not the core meaning.

Yes:

• Homo
  noun, nominative singular, from homo, hominis
  the subject

• sapiens
  adjective, nominative singular, from sapiens, sapientis
  agrees with homo

• mendacium
  noun, accusative singular, from mendacium, mendacii
  direct object of spernit

• spernit
  verb, 3rd person singular present active indicative, from spernere
  despises / rejects / scorns

• et
  conjunction
  and

• veritatem
  noun, accusative singular, from veritas, veritatis
  direct object of amat

• amat
  verb, 3rd person singular present active indicative, from amare
  loves