Ova bakterija se lako širi ako ljudi ne peru ruke dovoljno često.

Ova means this. It is the feminine singular form of the demonstrative adjective, and it matches bakterija because bakterija is a feminine singular noun.

So:

• ovaj = this (masculine)
• ova = this (feminine)
• ovo = this (neuter)

Because bakterija is feminine, Croatian uses ova bakterija = this bacterium / this bacteria.

In Croatian, every noun has a grammatical gender: masculine, feminine, or neuter. Bakterija is grammatically feminine, mainly because nouns ending in -a are very often feminine.

This is grammatical gender, not biological gender. So even though a bacterium is not female, the noun bakterija still behaves like a feminine noun.

Here se is a reflexive particle that is part of the verb expression širiti se, which means to spread.

So:

• širiti can mean to spread something
• širiti se means to spread in the sense of spreading by itself

In this sentence, bakterija se širi means the bacterium spreads or the bacteria spreads.

English often does not show this reflexive idea, but Croatian frequently does.

Širi is the 3rd person singular present tense form of širiti se.

It matches ova bakterija, which is singular:

• ja se širim = I spread
• ti se širiš = you spread
• on/ona/ono se širi = he/she/it spreads

So ova bakterija se lako širi literally means this bacterium spreads easily.

Lako means easily. It is an adverb, and it describes how the bacterium spreads.

So:

• širi se = spreads
• lako se širi or se lako širi = spreads easily

It tells you that the spreading happens without much difficulty.

Croatian word order is more flexible than English word order, but some patterns are more natural than others. In this sentence, se appears early because short unstressed words like se usually come near the beginning of the clause.

So Ova bakterija se lako širi is a very natural order.

You may also hear similar variations in other contexts, but se usually does not go at the very beginning of the sentence, and it often stays close to the verb.

Ako means if, and it introduces the condition.

So the structure is:

• main clause: Ova bakterija se lako širi
• if-clause: ako ljudi ne peru ruke dovoljno često

Literally: This bacterium spreads easily if people do not wash their hands often enough.

Croatian uses ako just like English uses if to introduce a condition.

Ljudi means people, and here it is the subject of the verb peru.

Because it is the subject, it is in the nominative plural form:

• singular: čovjek = person/man
• plural: ljudi = people

The verb must agree with this plural subject, which is why the sentence uses peru = they wash.

Yes, the infinitive is prati = to wash, but peru is its present-tense plural form.

This verb changes its stem in the present tense, so it does not look exactly like the infinitive. That is normal in Croatian.

Some forms are:

• ja perem = I wash
• ti pereš = you wash
• on/ona/ono pere = he/she/it washes
• mi peremo = we wash
• vi perete = you wash
• oni/one/ona peru = they wash

Since ljudi is plural, peru is the correct form.

In Croatian, negation with verbs is usually formed by putting ne before the verb as a separate word.

So:

• peru = they wash
• ne peru = they do not wash

This is the normal pattern in Croatian.

Ruke is the plural of ruka = hand. Here it is the direct object of peru, so it is in the accusative plural.

For this noun, the accusative plural looks the same as the nominative plural:

• singular: ruka
• plural nominative: ruke
• plural accusative: ruke

So peru ruke means wash hands.

Croatian often omits possessive words like their, his, or her when the meaning is obvious from context, especially with body parts.

So:

• ljudi peru ruke naturally means people wash their hands
• adding svoje is possible, but not necessary here

This is different from English, where wash hands often sounds incomplete without their in a sentence like this.

Dovoljno često means often enough.

Word by word:

• dovoljno = enough
• često = often

Croatian puts these in the order enough + often, while English usually says often enough.

So:

• ne peru ruke dovoljno često = do not wash their hands often enough

Croatian often uses the present tense for general truths, habits, and typical consequences, just like English does.

This sentence is not about one specific moment. It describes a general fact:

• if people do not wash their hands often enough, this bacterium spreads easily

So the present tense is the natural choice.

Yes. Croatian allows flexible clause order, so you can also say:

Ako ljudi ne peru ruke dovoljno često, ova bakterija se lako širi.

This means the same thing. The difference is mainly emphasis:

• original sentence starts with the result
• reversed version starts with the condition

Both are correct.

Š is pronounced like sh in English ship.

So:

• širi sounds roughly like shee-ree

This letter is very common in Croatian, and it always keeps that sh sound.