Ana explică regula.

Because explică is the 3rd person singular present tense form of the verb a explica (to explain).

Here is the present tense:

• eu explic = I explain
• tu explici = you explain
• el/ea explică = he/she explains

Since Ana is she, Romanian uses explică.

Romanian often omits subject pronouns when the subject is already clear from the verb form or from the noun used.

So instead of saying:

• Ea explică regula. = She explains the rule.

you can simply say:

• Ana explică regula.

The name Ana already tells you who is doing the action, so ea is unnecessary.

Regula means the rule.

The basic noun is:

• regulă = a rule

Romanian usually puts the definite article at the end of the noun, not as a separate word like English the.

So:

• regulă = a rule
• regula = the rule

This is a very important feature of Romanian grammar.

Because Romanian does not simply add -a to the end mechanically. The noun changes according to its pattern.

For this noun:

• regulă → regula

This is the normal definite singular form for many feminine nouns ending in -ă.

So you should learn it as a pattern:

• o regulă = a rule
• regula = the rule

Yes. In Ana explică regula, Ana is the subject and regula is the direct object.

• Ana = the person doing the action
• explică = the action
• regula = the thing being explained

So the structure is:

Subject + Verb + Object

which is also very common in Romanian.

Because pe is normally used before direct objects that are people or highly specific animate beings, not ordinary inanimate things.

For example:

• Văd regula. = I see the rule.
  No pe is used.

But:

• Văd pe Ana. = I see Ana.

Since regula is an inanimate noun, pe is not used here.

The normal and most neutral order is:

• Ana explică regula.

But Romanian word order is somewhat flexible, depending on emphasis.

For example:

• Regula o explică Ana. = It is Ana who explains the rule / Ana explains the rule.
• Explică Ana regula. = less neutral, possible in certain contexts

Still, for a beginner, Subject + Verb + Object is the safest pattern.

A useful approximation is:

• explică ≈ eks-PLEE-kuh

A few details:

• x is pronounced like ks
• the stress is on -pli-
• ă is a short central vowel, something like a very relaxed uh

So:

• ex-pli-că
• eks-PLEE-kuh

A good approximation is:

• regula ≈ REH-goo-lah

The stress is typically on the first syllable:

• RE-gu-la

And remember: this is regula (the rule), not regulă (a rule).

The infinitive is a explica, which means to explain.

In Romanian, dictionary forms of verbs usually appear with a:

• a explica = to explain
• a vorbi = to speak
• a învăța = to learn

So if you want to look up explică, you should look for a explica.

Because Ana is a proper name. Proper names usually do not take an article in this kind of sentence.

So:

• Ana explică regula.

not:

• The Ana explains the rule

English works similarly here: names usually do not need the.

Yes, in many contexts Romanian present tense can correspond to both:

• Ana explains the rule
• Ana is explaining the rule

The exact English translation depends on context.

Romanian often uses the simple present where English might choose either simple present or present continuous.

Yes. Ana explică regula. is a perfectly complete and natural sentence.

It has everything needed:

• a subject: Ana
• a verb: explică
• an object: regula

It sounds like a simple textbook example, but it is fully correct and natural Romanian.