Leo watoto wanavaa jezi nyekundu uwanjani.

Here is a word-by-word breakdown:

• Leo = today
• watoto = children
• wanavaa = are wearing / wear
• jezi = jersey / sports shirt
• nyekundu = red
• uwanjani = on the field / at the playground / in the grounds

So the sentence is built very transparently: Today children are wearing red jerseys on the field.

Swahili verbs normally include information about the subject and the tense inside the verb itself.

wanavaa can be divided like this:

• wa- = subject marker for they when the subject is people
• -na- = present tense marker
• -vaa = verb root meaning wear / put on

So:

wa + na + vaa = wanavaa

That means they are wearing or they wear.

The -na- in wanavaa is the usual present tense marker.

Depending on context, it can mean:

• are wearing
• wear
• sometimes a general present or ongoing present

In this sentence, because of Leo meaning today, it most naturally means something like are wearing today.

Because watoto is a plural noun referring to people.

In Swahili, nouns belong to noun classes, and verbs must agree with the noun class of the subject.

• mtoto = child
• watoto = children

For plural human nouns like watoto, the verb usually takes the subject marker wa-.

So:

• mtoto anavaa = the child is wearing
• watoto wanavaa = the children are wearing

Many Swahili loanwords, especially words borrowed from English, stay the same in both singular and plural.

So jezi can mean:

• a jersey
• jerseys

The context tells you which is meant.

In this sentence, because watoto is plural, English will usually translate the idea as red jerseys, even though jezi itself does not visibly change form.

In Swahili, adjectives usually come after the noun they describe.

So:

• jezi nyekundu = red jersey / red jerseys

This is the normal noun + adjective order in Swahili.

English says red jersey, but Swahili says the equivalent of jersey red.

Swahili adjectives often change form to agree with the noun class of the noun they describe.

jezi belongs to a class that commonly uses the adjective form nyekundu for red.

So:

• jezi nyekundu = red jersey / red jerseys

This agreement is normal Swahili grammar. Even though jezi does not change between singular and plural, the adjective form nyekundu is still the correct one for that noun class.

uwanjani comes from:

• uwanja = field, yard, ground, playground
• -ni = a locative ending meaning in / at / on

So uwanjani means something like:

• in the field
• on the field
• at the playground
• in the grounds

The exact English preposition depends on context. Swahili often uses one locative form where English has several different choices.

Time words like Leo are often placed at the beginning in Swahili to set the time frame right away.

So Leo watoto wanavaa jezi nyekundu uwanjani sounds very natural.

You could also move leo later in the sentence in some contexts, but putting it first is a very common and clear way to say Today, ...

Swahili does not have articles like a, an, and the.

So words like:

• watoto can mean children or the children
• jezi can mean a jersey, the jersey, or jerseys

English needs articles, but Swahili usually leaves that information to context.

Yes.

The present tense with -na- can be understood in more than one way depending on context. It can describe:

• something happening now
• something happening around now
• something people do regularly

So watoto wanavaa jezi nyekundu could mean:

• the children are wearing red jerseys
• the children wear red jerseys

In this sentence, Leo pushes the meaning toward what is happening today.

Yes, and the meaning would be slightly different.

• wanavaa focuses more on the action or present-time wearing
• wamevaa often means have put on or are dressed in

So:

• watoto wanavaa jezi nyekundu = the children are wearing / wear red jerseys
• watoto wamevaa jezi nyekundu = the children have red jerseys on / are dressed in red jerseys

In everyday speech, wamevaa is often very natural when you are describing what someone already has on.