Mimi nina wasiwasi sana leo.

Because mimi adds emphasis.

• Nina wasiwasi sana leo = a neutral way to say it
• Mimi nina wasiwasi sana leo = I am very worried today, perhaps contrasting with someone else or stressing your own feeling

So mimi is not required, but it is perfectly correct.

Yes. In fact, Nina wasiwasi sana leo is often the more natural everyday version.

Swahili verbs already show the subject, so the separate subject pronoun is usually omitted unless you want emphasis, contrast, or clarity.

Nina is made of:

• ni- = I
• na = with / have

So nina literally works like I have or I am with.

In standard spelling, it is written as one word: nina, not ni na in this sentence.

This is a very common Swahili pattern. Swahili often uses a noun after nina to express a state or feeling.

For example:

• nina njaa = I am hungry
• nina kiu = I am thirsty
• nina wasiwasi = I am worried / anxious

So even though the structure looks like have, the natural English meaning is often am + adjective.

Wasiwasi means worry, anxiety, or concern.

In this sentence, it describes an emotional state, so the whole expression means something like:

• I am worried
• I am anxious
• I feel a lot of concern

The exact English choice depends on context.

No. It is just the normal form of the word.

Even though it has a repeated sound pattern, that does not mean it is plural here. Learners sometimes notice the repetition and wonder about it, but wasiwasi is simply the word for worry/anxiety.

Sana means very or a lot.

So:

• wasiwasi sana = very worried / a lot of anxiety

It strengthens the feeling.

In Swahili, words like sana usually come after the word or phrase they intensify.

So:

• wasiwasi sana = very much worry / very worried

That word order is normal in Swahili.

Leo means today.

Swahili does not need a preposition like on here. You simply say leo.

So:

• leo = today

not something like on today.

Yes. Swahili word order is somewhat flexible, especially with time words.

All of these are natural:

• Nina wasiwasi sana leo
• Leo nina wasiwasi sana
• Mimi nina wasiwasi sana leo

The meaning stays basically the same, though the emphasis may shift a little.

Usually it means I am worried today or I am very anxious today.

Because wasiwasi is an abstract noun, the sentence normally describes your emotional state, not a countable number of separate worries.

Still, depending on context, it can also suggest that many concerns are on your mind.

They are related, but not the same:

• wasiwasi = worry, anxiety, unease
• hofu = fear

So nina wasiwasi is closer to I am worried/anxious, while nina hofu is closer to I am afraid.

A simple pronunciation guide is:

• Mimi = MEE-mee
• nina = NEE-na
• wasiwasi = wa-see-WA-see
• sana = SA-na
• leo = LEH-o

A useful stress pattern is:

MI-mi NI-na wa-si-WA-si SA-na LE-o

A few helpful pronunciation points:

• Swahili vowels are usually clear and pure
• every vowel is pronounced
• leo has two vowel sounds: le-o, not one merged sound like English lee-oh squeezed together too much