Si tibi consilio opus est, magistram ipsam interroga.

Because tibi is the dative singular form of tu, meaning to you or for you.

In this sentence, Latin is not saying simply you need advice in the same way English does. Instead, it uses the idiom opus est, which works more like:

• there is need for advice to you
• or more naturally, you need advice

So the person who has the need appears in the dative: tibi = for you / to you.

Because opus est regularly takes the thing needed in the ablative.

So:

• consilio opus est = there is need of advice
• more naturally: advice is needed

This is a standard Latin construction. English speakers often expect a direct object, but Latin handles it differently here.

So the pattern is:

• mihi aqua opus est = I need water
• nobis auxilio opus est = we need help
• tibi consilio opus est = you need advice

Opus est is an idiomatic expression meaning there is need or, more naturally in English, someone needs something.

It is made up of:

• opus = need (here functioning like a noun)
• est = is

So literally tibi consilio opus est is something like:

• there is need of advice for you

But good English is:

• if you need advice

This is one of those expressions that is best learned as a unit.

Latin often has more than one way to express an idea. Here, opus est is a very common and natural way to say need.

A learner may be tempted to translate word-for-word from English, but Latin frequently prefers its own idioms. So si tibi consilio opus est is a very normal way to say:

• if you need advice

It is usually best to recognize opus est as a standard Latin construction rather than forcing English structure onto it.

Because magistram is the direct object of interroga.

The verb interroga means ask. The person being asked is put in the accusative:

• magistra = teacher as the subject form
• magistram = teacher as the direct object

So:

• magistram interroga = ask the teacher

Ipsam adds emphasis. It agrees with magistram and means something like:

• the teacher herself
• the teacher in person
• the very teacher

So magistram ipsam interroga is stronger than just magistram interroga.

It suggests something like:

• ask the teacher herself
• ask the teacher directly

This often implies that the teacher is the best source of the advice.

Because ipsam is modifying magistram, so it must agree with it in:

• gender: feminine
• number: singular
• case: accusative

That is standard adjective/pronoun agreement in Latin.

So:

• magistram = accusative feminine singular
• ipsam = accusative feminine singular

Even though ipse, ipsa, ipsum is often translated as self or very, it still behaves grammatically like a word that must agree with the noun it emphasizes.

Interroga is the second person singular present active imperative of interrogo, interrogare.

That means it is a command addressed to one person:

• interroga = ask!

If the command were addressed to more than one person, the plural imperative would be:

• interrogate = ask! (to more than one person)

So this sentence is speaking to a single person: If you need advice, ask the teacher herself.

Latin word order is more flexible than English word order because the endings show the grammatical relationships.

Placing interroga at the end is perfectly natural and can give the command a nice sense of emphasis or completion. Latin often places an important verb at the end of the clause.

So:

• magistram ipsam interroga

is a natural Latin way to say:

• ask the teacher herself

Even though English usually wants the verb earlier, Latin does not need to follow the same order.

Yes. English advice is an uncountable noun, but Latin consilium is a regular noun and can appear in the singular.

Here consilio means advice, guidance, or counsel in a general sense. So the singular is completely normal.

In other words, Latin is not necessarily talking about one piece of advice. It is just using its own noun system in the ordinary way.

Yes. Magistra is feminine, and magistram ipsam shows that clearly.

So the sentence is referring to a female teacher:

• magistram = accusative singular feminine
• ipsam = accusative singular feminine agreeing with it

If the teacher were male, Latin would use:

• magistrum ipsum interroga = ask the teacher himself

It has two parts:

1. Si tibi consilio opus est
   = If you need advice

2. magistram ipsam interroga
   = ask the teacher herself

This is a basic if-clause + main clause sentence:

• si introduces the condition
• the second part gives the result or instruction

So the overall structure is:

• If X, then do Y

Here:

• If you need advice, ask the teacher herself.