Apiarius ramum apiastro oblinit.

Because apiarius is in the nominative singular, the case normally used for the subject of a finite verb.

So in this sentence:

• apiarius = the beekeeper = subject
• oblinit = smears/coats = verb

Latin often tells you grammatical roles through endings, not just word order.

Because ramum is accusative singular of ramus, meaning branch.

The accusative case is commonly used for the direct object, the thing directly affected by the action. Here, the branch is what the beekeeper is smearing/coating.

So:

• ramus = branch, as a dictionary form
• ramum = branch, as the direct object

Apiastro is ablative singular, from apiāstrum.

Here the ablative is being used as an ablative of means/instrument: it tells you what the branch is being smeared with.

So the sense is:

• ramum apiastro oblinit = he smears the branch with bee-balm

In English, we often use with for this idea, but Latin can express it with the ablative alone.

In form, yes: for a second-declension noun, dative singular and ablative singular can look the same.

But in this sentence, the meaning and construction show that it is ablative, not dative.

Why?

• oblinit takes a direct object: ramum
• apiastro names the substance or instrument used
• that is a normal job for the ablative of means/instrument

A dative meaning would not fit naturally here.

Because Latin often does not need a preposition when the ablative of means/instrument is used.

English says:

• smears the branch with bee-balm

Latin can simply say:

• ramum apiastro oblinit

The case ending on apiastro already shows the relationship.

Oblinit is:

• third person singular
• present tense
• indicative mood
• active voice

So it means he/she/it smears or coats.

Because the subject is apiarius, the natural translation is the beekeeper smears.

The dictionary form is oblinō or, if you are identifying the conjugation, oblinere.

From that verb:

• oblinō = I smear, coat
• oblinit = he/she/it smears, coats

This is a common thing in Latin: the form you see in a sentence is often not the same as the form you would look up in a dictionary.

Because the verb ending already tells you the subject is third person singular.

In oblinit, the -it ending means he/she/it. Latin does not need to add a separate pronoun unless it wants extra emphasis or contrast.

So:

• oblinit already means he smears, she smears, or it smears
• the noun apiarius tells you exactly who that he is

Because Classical Latin has no articles.

English distinguishes between:

• a branch
• the branch

Latin usually leaves that unstated unless the context makes it clear. So ramum can mean either a branch or the branch, depending on context.

The same applies to apiarius:

• a beekeeper
• the beekeeper

Latin relies much more on context than English does for this.

Less than in English. Latin word order is flexible, because the endings show the grammatical roles.

In this sentence:

• apiarius = subject
• ramum = direct object
• apiastro = ablative of means
• oblinit = verb

Even if the order changed, the endings would still tell you who is doing what.

That said, the order is not meaningless. Latin word order often affects emphasis or style. Here, the sentence has a very normal feel, with the verb placed at the end, which is common in Latin prose.

All three nouns here are from the second declension, but they are not all the same gender.

• apiarius: second declension, masculine, nominative singular
• ramus: second declension, masculine; here it appears as ramum, accusative singular
• apiāstrum: second declension, neuter; here it appears as apiastro, ablative singular

So this sentence is a nice example of how second-declension nouns can have different genders and different case endings.

Yes, they are related in origin: both are connected with bees.

• apiarius = beekeeper
• apiāstrum = a plant associated with bees, often identified as bee-balm or lemon balm

So even though they are different words with different grammatical roles, they share the same general semantic area. That can help you remember them, but you still need to treat them as separate vocabulary items.