אני רוצה להחליף את הסדין, כי הוא לא נקי.

Not in this unpointed spelling.

In everyday Hebrew writing without vowel marks, רוצה can be read as:

• rotse if the speaker is male
• rotsa if the speaker is female

So the written sentence could be said by either a man or a woman. In speech, the pronunciation tells you the gender.

After רוצה (want), Hebrew normally uses an infinitive, just like English uses to + verb.

So:

• אני רוצה להחליף = I want to change / replace
• literally: I want to-change

This is a very common pattern:

• אני רוצה לאכול = I want to eat
• אני רוצה ללכת = I want to go

להחליף can mean to replace, to change, to switch, or to exchange, depending on context.

In this sentence, the most natural meaning is to change or to replace the sheet.

Examples:

• להחליף בגדים = to change clothes
• להחליף סדין = to change a sheet
• להחליף מקום = to switch places

את marks a definite direct object.

It does not have its own English translation here, but it tells you that the noun after it is the specific thing being acted on.

So:

• להחליף את הסדין = to change the sheet
• להחליף סדין = to change a sheet

A very important rule:

• use את before a definite direct object
• do not use את before an indefinite one

Since הסדין means the sheet, it needs את.

The prefix ה־ is the Hebrew word the.

So:

• סדין = a sheet
• הסדין = the sheet

The sentence is talking about a specific sheet, probably the one currently on the bed, so Hebrew uses the definite form.

In Hebrew, pronouns are based on grammatical gender, not just biological sex.

The noun סדין is grammatically masculine, so when you refer back to it, you use הוא.

So here:

• הסדין = the sheet
• הוא = it/he, referring to that masculine noun

In English we say it, but Hebrew uses the same word form that is also used for he.

If the noun were feminine, Hebrew would use היא.

Because adjectives in Hebrew agree with the noun they describe in gender and number.

סדין is masculine singular, so the adjective must also be masculine singular:

• נקי = clean (masculine singular)

Compare:

• הסדין נקי = the sheet is clean
• החולצה נקייה = the shirt is clean (feminine singular)
• הסדינים נקיים = the sheets are clean (masculine plural)

So הוא לא נקי means it is not clean, with the adjective matching סדין.

Here כי means because.

So:

• כי הוא לא נקי = because it is not clean

A useful note: כי can also mean that in some contexts, but in this sentence the meaning is clearly because.

Sometimes, but אני is often kept for clarity.

In present tense, Hebrew verb forms do not clearly show person the way English does. רוצה by itself could mean something like:

• I want
• you want
• he wants
• she wants

depending on context and pronunciation.

So including אני makes the sentence clear:

• אני רוצה להחליף את הסדין

In casual speech, pronouns can sometimes be dropped if the context is obvious, but learners should usually keep them.

Usually, yes.

סדין most commonly means a bedsheet or sheet in the bedding sense. In this sentence, that is definitely the natural meaning.

Depending on context, English might say:

• sheet
• bed sheet
• bedsheet

But in normal use, סדין strongly suggests bedding.

A natural pronunciation is:

• ani rotse lehachlif et hasadin, ki hu lo naki
  if the speaker is male

• ani rotsa lehachlif et hasadin, ki hu lo naki
  if the speaker is female

A rough breakdown:

• אני = ani
• רוצה = rotse / rotsa
• להחליף = lehachlif
• את = et
• הסדין = hasadin
• כי = ki
• הוא = hu
• לא = lo
• נקי = naki

Because Hebrew usually uses a pronoun plus adjective in this kind of sentence.

So:

• הוא לא נקי = it is not clean

In the present tense, Hebrew often has no separate word for is in ordinary sentences. So literally, it is more like:

• he/it not clean

But in natural English, we translate it as it is not clean.

This is very normal in Hebrew:

• הוא גדול = it/he is big
• היא יפה = she/it is beautiful
• הם עייפים = they are tired