Humanitas et comitas hospitem laetum faciunt, etiam si domus parva est.

Because the subject is Humanitas et comitas — humanitas plus comitas, joined by et (and). Two singular nouns joined by and make a plural subject, so the verb must be plural: faciunt = they make.

Latin often uses singular abstract nouns to talk about a quality in a general way. So:

• humanitas = kindness, humanity, cultivated courtesy
• comitas = courtesy, affability, friendliness

They are singular because each word names one abstract quality. English does the same thing: we also say kindness is important or friendliness helps.

Because hospitem is the direct object of faciunt.

The verb facere means to make or to do. Here it means make in the sense cause someone to become something. The person affected by the action is put in the accusative:

• hospitem = the guest as the object

So humanitas et comitas hospitem ... faciunt = kindness and friendliness make the guest ...

Because laetum goes with hospitem.

In Latin, after verbs like facere (to make), you often get:

• an object in the accusative
• plus a word describing what that object becomes, also in the accusative

So:

• hospitem = accusative singular masculine
• laetum = accusative singular masculine

They match because laetum describes hospitem: make the guest happy.

This is often called a predicate accusative or object complement.

By itself, yes, that combination could simply mean the happy guest in the accusative case.

But in this sentence, because it follows faciunt, the natural meaning is:

• they make the guest happy

So the grammar of the whole sentence tells you that laetum is the result of the action, not just a normal adjective attached to guest.

Because laetum agrees with hospitem, not with the subject.

• hospitem is accusative singular masculine
• so the adjective describing it must also be accusative singular masculine: laetum

If it were laetus, that would be nominative singular masculine, which would not match hospitem.

Etiam si means even if or even though.

It introduces a clause that adds a contrast:

• Humanitas et comitas hospitem laetum faciunt
• etiam si domus parva est

So the sense is: the guest is made happy by kindness and friendliness, even if the house is small.

In many contexts, etiam si is best understood as even if, but in a sentence like this it can feel very close to even though.

Because the subject of that clause is domus, which is singular:

• domus parva est = the house is small

So even though the main clause has a plural verb (faciunt), the subordinate clause has its own subject and its own verb, and that verb is singular.

Both are nominative singular, because they form the subject and predicate adjective of est:

• domus = nominative singular
• parva = nominative singular feminine, agreeing with domus

So:

• domus parva est = the house is small

Yes. Domus is a somewhat irregular noun in Latin.

A few useful things to know:

• it is usually feminine
• it belongs mainly to the fourth declension
• but it also shows some forms that look more like the second declension

In this sentence, though, you only need the basic fact that domus is nominative singular and means house or home.

The main clause is:

Humanitas et comitas hospitem laetum faciunt

A helpful way to analyze it is:

• Humanitas et comitas = subject
• hospitem = direct object
• laetum = object complement / predicate accusative
• faciunt = verb

So the pattern is:

subject + object + result word + verb

That is a very common Latin pattern with facere: someone/something makes someone/something + adjective/noun

Yes. Latin word order is much freer than English word order because the endings show how the words function.

For example, Latin could rearrange this sentence in various ways and still mean basically the same thing. The current order is natural and clear, but not the only possibility.

This order puts Humanitas et comitas first, which gives emphasis to the qualities that really matter. Then the result comes at the end of the main clause with faciunt.

They are similar, but not identical.

• humanitas often suggests humanity, kindness, cultured feeling, or considerate behavior
• comitas often suggests courtesy, graciousness, pleasant friendliness, or affability

So the pair gives a fuller idea than either word alone: not just polite behavior, but genuinely warm and civilized treatment of the guest.