Studiamo la teoria oggi.

In Italian, subject pronouns are often omitted because the verb ending already shows who is doing the action.

• studiamo = we study / we are studying
• The ending -iamo tells you the subject is we.

So Noi studiamo la teoria oggi is possible, but noi is usually unnecessary unless you want emphasis or contrast:

• Noi studiamo la teoria oggi, loro domani.
  We study theory today, they tomorrow.

Studiamo is the 1st person plural present tense of studiare (to study).

Conjugation of studiare in the present:

• io studio = I study
• tu studi = you study
• lui/lei studia = he/she studies
• noi studiamo = we study
• voi studiate = you all study
• loro studiano = they study

So studiamo specifically means we study or we are studying.

It can mean both.

Italian uses the simple present tense in many situations where English uses either:

• we study
• we are studying

So Studiamo la teoria oggi can mean:

• We study theory today
• We are studying theory today

Context tells you which is more natural.

Italian uses definite articles more often than English does.

Here, la teoria means the theory, but in many cases Italian would still use the article where English might not:

• Studio la matematica. = I study math.
• Mi piace la musica. = I like music.

So la teoria is normal Italian. Omitting the article here would usually sound incomplete or unnatural.

La shows that teoria is:

• singular
• feminine

That is why the article is la, not il.

Examples:

• la teoria = the theory
• il libro = the book

So when you learn nouns in Italian, it is very helpful to learn them with their article:

• la teoria
• not just teoria

Putting oggi at the end is a very natural word order in Italian.

Italian word order is more flexible than English. These are all possible:

• Studiamo la teoria oggi.
• Oggi studiamo la teoria.
• La teoria la studiamo oggi.

They all mean roughly the same thing, but the emphasis changes a little:

• Studiamo la teoria oggi = neutral
• Oggi studiamo la teoria = emphasis on today
• La teoria la studiamo oggi = emphasis on theory

Yes, absolutely. That is very common.

Placing oggi first emphasizes the time:

• Oggi studiamo la teoria. = Today we are studying theory.

This is often the most natural order if you want to highlight today.

It is pronounced roughly stoo-DYAH-mo.

A few helpful points:

• stu sounds like stoo
• dia in studiamo sounds like dyah
• stress falls on dia: stu-DIA-mo

So:

• studiamo → stoo-DYAH-mo

Yes, sometimes.

The 1st person plural form can also be used as an exhortation, similar to let’s ...:

• Studiamo! = Let’s study!

But in Studiamo la teoria oggi, the most likely reading is simply we study / we are studying theory today. Intonation and context decide whether it is a statement or a suggestion.

It can be interpreted as either, depending on context.

Italian present tense is often used for scheduled or planned future actions, especially with a time word like oggi:

• Oggi studiamo la teoria.

This could mean:

• we are studying it today right now / later today
• we will study it today, as part of today’s plan

English does something similar:

• Today we study theory
• Today we’re studying theory

Because oggi is an adverb meaning today.

Adverbs of time like oggi, domani, and ieri usually do not need a preposition:

• oggi = today
• domani = tomorrow
• ieri = yesterday

So you say:

• Studiamo la teoria oggi. not
• Studiamo la teoria in oggi.

Yes:

• Noi studiamo la teoria oggi.

This is grammatically correct, but it usually sounds more emphatic than the version without noi.

You would use noi if you want to:

• contrast with someone else
• stress that we, specifically, are doing it

For example:

• Noi studiamo la teoria oggi, voi fate pratica.
  We study theory today, you do practice.

Often yes, but the exact nuance depends on context.

Teoria can refer to:

• theory in an academic or intellectual sense
• the theoretical part of a subject, as opposed to practice

For example, in a classroom context:

• Studiamo la teoria oggi, la pratica domani.
  We study the theory today, the practical part tomorrow.

So it can mean not only abstract theory, but also the theoretical material of a course or topic.