Dobânda contului de economii este mică.

Because dobânda means the interest, while dobândă means interest in a general/indefinite sense.

Romanian often adds the definite article to the end of the noun instead of using a separate word like the in English.

• dobândă = interest
• dobânda = the interest

So Dobânda contului de economii... literally starts with The interest of the savings account...

Contului is the genitive/dative singular form of contul (the account).

Here it is used because Romanian is expressing possession:

• dobânda contului = the account’s interest / the interest of the account

Breakdown:

• cont = account
• contul = the account
• contului = of the account / to the account

So in this sentence, contului shows that the interest belongs to the account.

Because de economii specifies what kind of account it is: a savings account.

• cont = account
• de economii = for savings / of savings

Together:

• cont de economii = savings account
• contului de economii = of the savings account

This is a very common Romanian structure: noun + de + noun.

Examples:

• carte de istorie = history book
• periuță de dinți = toothbrush
• cont de economii = savings account

Romanian usually expresses definiteness by attaching it to the noun, not by using a separate article.

In this sentence:

• dobânda = the interest
• contului = of the account

English uses separate words:

• the interest of the savings account

Romanian often does not need a separate the. The endings on the nouns already carry that information.

Also, in a genitive phrase like this, definiteness is often shown on the noun form itself:

• contului already means of the account

Because mică must agree with dobânda, which is a feminine singular noun.

Agreement in Romanian means the adjective changes form to match the noun’s:

• gender
• number
• sometimes definiteness/context

Here:

• dobândă is feminine singular
• so the adjective must also be feminine singular: mică

Compare:

• dobânda este mică = the interest is low/small
• prețul este mic = the price is low/small

So:

• mic = masculine singular
• mică = feminine singular

Because Romanian often uses mic / mică where English would naturally use low.

So even though mică literally looks like small, in this context it means low.

Examples:

• preț mic = low price
• salariu mic = low salary
• dobândă mică = low interest

This is a normal Romanian way to express a low amount or level.

Este means is. It is the 3rd person singular form of the verb a fi (to be).

So:

• este = is

In the sentence:

• Dobânda contului de economii este mică.
• The interest of the savings account is low.

Romanian usually keeps este in this kind of sentence, just like English uses is.

Yes, but the given order is the most neutral and natural.

Standard order:

• Dobânda contului de economii este mică.

You might also hear variations for emphasis, such as:

• Mică este dobânda contului de economii.
  This sounds marked or stylistic, with emphasis on mică.

For learners, it is best to stick with:

• subject + este + adjective

So the sentence structure is:

• Dobânda contului de economii = subject
• este = verb
• mică = predicate adjective

De economii here is a fixed expression meaning for savings.

It comes from:

• economie = economy / saving
• economii = savings

So:

• cont de economii = savings account

This is different from an adjective like economic:

• economic = economical / economic
• economice = feminine/plural forms depending on context

So:

• cont de economii = savings account
• cont economic would mean something more like economical account, which is not the normal term

A rough pronunciation guide is:

doh-BUHN-da kon-TOO-looy de eh-ko-noh-MEE yees-te MEE-kuh

A few useful notes:

• â is a central vowel, somewhat like a muted uh sound, but it has no exact English equivalent.
• ui in contului is pronounced as part of one flowing ending: -looy
• ii in economii is usually pronounced like a long ee sound here
• că at the end of mică sounds like kuh

Most often, yes, especially in everyday and financial contexts.

• dobândă = interest, usually financial interest
• rată a dobânzii = interest rate

In this sentence, it clearly refers to bank interest because of contului de economii (savings account).

So a learner should understand:

• dobândă in this context = the money the bank pays (or charges) as interest

Yes, you may hear that too, and it can sound natural in conversation.

Compare:

• Dobânda contului de economii este mică.
  More formal or compact; literally the interest of the savings account
• Dobânda la contul de economii este mică.
  Also natural; literally the interest on the savings account

The original sentence is grammatically very good and slightly more formal or written in style.