Canis humi dormit ante ostium cenaculi.

Because canis is the subject of dormit, so it is in the nominative singular.

• canis = dog
• nominative singular = the dog as the one doing the action

This noun belongs to the third declension, and its nominative singular happens to be canis.

Dormit is:

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

So it means he/she/it sleeps or simply is sleeping, depending on context.

Because the subject is canis (dog), dormit means the dog sleeps.

Humi is a special old case form called the locative, and here it means on the ground or on the floor.

Some Latin words for places can use this special form without a preposition. So instead of saying something like on the ground with a separate preposition, Latin can simply say humi.

This is similar in idea to forms like:

• domi = at home
• ruri = in the countryside

So humi dormit means sleeps on the ground/floor.

It is a real and standard Latin form, but it is a little special, so yes, it is something worth memorizing.

It comes from humus, meaning ground, earth, or soil. The locative humi means on the ground.

A learner should especially remember it because it does not look like the more regular case patterns you may expect.

Because ante is a preposition that normally takes the accusative when it means before or in front of.

So:

• ante = before / in front of
• ostium = accusative singular of ostium

Together, ante ostium means in front of the door.

Cenaculi is in the genitive singular, showing possession or close relationship.

• ostium = door
• cenaculi = of the dining room or of the upper room

So ostium cenaculi means the door of the dining room.

This is a very common Latin pattern:

• noun + genitive
• door of the room
• house of the farmer
• book of the girl, etc.

Cenaculum originally refers to an upper room. In many contexts it can also mean a dining room, since dining could take place in such a room.

So cenaculi could be understood as:

• of the dining room
• of the upper room

The exact best English meaning depends on context.

Because cenaculi is a genitive singular form, and it naturally attaches to a noun like ostium to mean the door of the dining room.

So the structure is:

• ante
  • ostium cenaculi
• in front of
  • the door of the dining room

You should read ostium cenaculi as one noun phrase.

Latin has no articles like English the or a/an.

So:

• canis can mean a dog or the dog
• ostium can mean a door or the door

Which one sounds best in English depends on context. Latin leaves that unstated unless something else makes it clear.

Latin word order is much freer than English word order because the endings show the grammatical relationships.

English depends heavily on order:

• The dog sleeps...

Latin can move words around more easily because:

• canis shows the subject
• ostium is marked by the preposition ante
• cenaculi shows possession
• dormit shows the verb

This sentence is perfectly natural. A Latin writer may choose the order for rhythm, emphasis, or style rather than strict subject-verb-object order.

Yes. Canis can be used for either a male or female dog, depending on context.

Grammatically, it is often treated as a noun of common gender when referring to a real dog whose sex may or may not matter.

So the sentence itself does not tell you whether the dog is male or female.

Here it is accusative singular.

A learner may hesitate because neuter nouns can have forms that look similar across cases, but here the structure helps:

• ante takes the accusative
• ostium is the accusative singular of ostium
• the plural would be ostia

So ante ostium means in front of the door, not in front of the doors.

Yes. Ante can mean:

• before in time
• in front of in space

In this sentence it is clearly spatial, because it is followed by ostium cenaculi and describes where the dog is sleeping.

So here ante ostium cenaculi means in front of the door of the dining room.

It can be either, depending on context.

Because the sentence also mentions the door of the dining room, many readers may naturally think on the floor inside or near a building. But the Latin form itself basically means on the ground / on the floor, that is, down low on the earth or surface, not on a bed or raised place.

So the exact English wording depends on the situation you imagine.