אני צריך להביא עוד כיסא אחד, כי יש כמה אורחים הערב.

Hebrew has no indefinite article, so there is no separate word for a/an.

So כיסא by itself can mean a chair. In this sentence, כיסא אחד means one chair. Depending on context, English may translate that as one chair or a chair, but in Hebrew אחד is the number one, not an article.

By contrast, Hebrew does have a definite article: ה-, as in הערב.

Not exactly in the same way as a normal verb like מביא or הלך. In Modern Hebrew, צריך is often treated as a modal-like word meaning need / have to, and it behaves a lot like an adjective in the present tense.

That is why it changes for gender and number:

• צריך = masculine singular
• צריכה = feminine singular
• צריכים = masculine plural
• צריכות = feminine plural

So אני צריך להביא means I need to bring.

It could, in some contexts, but אני helps make the subject clear.

In the present tense, צריך does not show person. By itself, צריך could mean:

• I need (if the speaker is masculine singular)
• you need (masculine singular)
• he needs

So adding אני removes ambiguity. This is very common in Hebrew.

Because the form agrees with the speaker's gender.

• A male speaker says אני צריך
• A female speaker says אני צריכה

So the sentence as written sounds like it is being said by a man. If a woman were speaking, it would be:

אני צריכה להביא עוד כיסא אחד, כי יש כמה אורחים הערב.

After צריך, Hebrew normally uses the infinitive, and Hebrew infinitives usually begin with ל-.

So:

• להביא = to bring
• צריך להביא = need to bring

This is the normal pattern:

• אני רוצה לאכול = I want to eat
• אני יכול לבוא = I can come
• אני צריך להביא = I need to bring

Here עוד means another / one more / an additional.

So עוד כיסא אחד means one more chair.

But עוד is a very flexible word in Hebrew. In other contexts it can also mean:

• more
• still
• yet
• another

Its exact meaning depends on context.

Because in Hebrew, the number one usually comes after the noun:

• כיסא אחד = one chair
• ילד אחד = one boy
• דירה אחת = one apartment

This is different from English.

A useful thing to remember is that אחד / אחת often come after the noun, while many other numbers usually come before it.

Yes. עוד כיסא is perfectly natural and often enough.

The version with אחד makes it a little more explicit that the speaker needs exactly one more chair.

So:

• עוד כיסא = another chair / one more chair
• עוד כיסא אחד = one more chair, with a bit more emphasis on one

כי introduces a full clause, so it fits well here:

• כי יש כמה אורחים הערב = because there are several guests tonight

בגלל usually means because of and is normally followed by a noun phrase, not a full clause:

• בגלל האורחים = because of the guests

In everyday speech, people do say בגלל ש- before a clause, but כי is the simpler and more standard choice here.

יש means there is / there are or more literally there exists / there exist.

In this sentence:

• יש כמה אורחים = there are several guests

A very important point is that יש does not change for singular vs. plural:

• יש כיסא = there is a chair
• יש אורחים = there are guests

So even though English changes from is to are, Hebrew still uses יש.

Because כמה can mean two different things depending on context:

• in a question: how many
• in a statement: several / a few / some

So here כמה אורחים does not mean how many guests? It means several guests.

This is very common in Hebrew.

Because after כמה, Hebrew normally uses a plural noun:

• כמה אנשים = several people
• כמה ספרים = several books
• כמה אורחים = several guests

So כמה אורח would sound wrong in normal Modern Hebrew.

אורחים is the masculine plural form of guest.

In Hebrew, the masculine plural is used for:

• a group of men
• a mixed group
• a group whose gender is unknown or not important

If the guests were all women, you would say:

• כמה אורחות

So the sentence as written suggests male guests, mixed guests, or simply uses the default masculine plural.

הערב here means this evening / tonight.

Literally, it is the evening, but in Hebrew that often works like English tonight or this evening, depending on context.

The ה- is the definite article the.

Compare:

• הערב = tonight / this evening
• בערב = in the evening
• ערב = evening

So הערב in this sentence is a time expression meaning tonight.