Umycie rąk przed obiadem jest ważne.

Umycie is a verbal noun. It comes from the verb umyć, which means to wash in the sense of to wash completely / to get something washed.

So umycie rąk literally means the washing of hands or more naturally washing one’s hands.

In this sentence, umycie rąk przed obiadem is the whole subject of the sentence.

Both are possible, but they are not exactly the same.

• umycie comes from umyć (perfective)
• mycie comes from myć (imperfective)

Very roughly:

• mycie rąk = hand-washing as an activity, process, or habit
• umycie rąk = washing the hands properly / getting them washed, often seen as a completed act

So:

• Mycie rąk przed obiadem jest ważne = Washing hands before lunch is important
• Umycie rąk przed obiadem jest ważne = Washing your hands before lunch is important, with a slightly stronger sense of the act being completed

In everyday use, both can sound natural, but umycie stresses the completed result a bit more.

Because after this kind of verbal noun, Polish often uses the genitive case for the thing affected by the action.

• ręce = nominative/accusative plural
• rąk = genitive plural

So:

• umycie rąk = washing of hands

This is similar to how English can say the washing of hands, where hands is not the grammatical subject but the thing being washed.

A learner often expects something like the direct object form used with the verb:

• umyć ręce = to wash hands

But once the verb becomes a noun:

• umycie rąk = the washing of hands

the case changes.

Because the preposition przed here requires the instrumental case.

• obiad = nominative
• obiadem = instrumental

So:

• przed obiadem = before lunch / before dinner

This is a fixed grammar pattern:

• przed śniadaniem = before breakfast
• przed kolacją = before supper/dinner
• przed snem = before sleep / before going to bed

So the form obiadem is there because przed demands it.

Because the subject of the sentence is umycie rąk przed obiadem, and the head word of that subject is umycie, which is neuter singular.

Polish adjectives must agree in gender and number with what they describe.

• ważny = masculine singular
• ważna = feminine singular
• ważne = neuter singular

Since umycie is neuter, we get:

• Umycie ... jest ważne

Jest means is.

So the structure is:

• Umycie rąk przed obiadem = subject
• jest = is
• ważne = important

Polish sometimes omits to be in the present tense, but in this type of standard statement, jest is normally used:

• Umycie rąk przed obiadem jest ważne.

Without jest, it would sound incomplete or unnatural here.

Yes, it is grammatical and natural.

It sounds a bit formal or instructional, which fits contexts like:

• hygiene advice
• school rules
• parenting guidance
• public health messages

In everyday speech, people might also say more directly:

• Ważne jest umycie rąk przed obiadem.
• Trzeba umyć ręce przed obiadem. = You need to wash your hands before lunch.
• Należy umyć ręce przed obiadem. = more formal, One should wash one’s hands before lunch.

Yes. Polish word order is fairly flexible, though the most neutral version here is:

• Umycie rąk przed obiadem jest ważne.

You could also say:

• Ważne jest umycie rąk przed obiadem.

This puts a bit more focus on important.

You could move przed obiadem earlier too, but that may sound more marked:

• Przed obiadem umycie rąk jest ważne.

That version emphasizes the before lunch part more strongly.

So the original sentence is probably the best neutral teaching example.

That depends on context and on cultural usage.

In Polish, obiad is the main cooked meal of the day. In many contexts, it corresponds best to lunch, but sometimes English speakers may feel dinner is a better translation.

So przed obiadem can be understood as:

• before lunch
• sometimes before dinner, depending on the household schedule

This is more a vocabulary/culture point than a grammar issue.

Not in the same way. Polish usually prefers a verbal noun or another structure rather than using the infinitive as the subject quite so directly.

That is why:

• Umycie rąk przed obiadem jest ważne.

sounds natural.

Other natural options are:

• Ważne jest, żeby umyć ręce przed obiadem. = It is important to wash your hands before lunch.
• Trzeba umyć ręce przed obiadem. = You should wash your hands before lunch.

So Polish often chooses different grammar than English for this kind of statement.

Polish often leaves possession understood when it is obvious from context, especially with body parts.

So:

• umycie rąk literally = washing of hands
• natural meaning = washing your hands / washing one’s hands

Polish does have possessive words like swoich or twoich, but they are usually unnecessary here.

For example:

• Umycie swoich rąk przed obiadem jest ważne sounds unnatural or overly explicit in most contexts.

So leaving out your is normal Polish usage.