אני נוסע לעבודה באוטובוס, אבל היא נוסעת ברכבת.

Because Hebrew present-tense verb forms agree with gender as well as number.

• אני means I, but it does not tell you whether the speaker is male or female.
• נוסע is the masculine singular form.
• נוסעת is the feminine singular form.

So this sentence tells you that the speaker is male, while היא refers to a female, so her form is also feminine:

• אני נוסע = I am traveling / I go
• היא נוסעת = she is traveling / she goes

She would say:

אני נוסעת לעבודה באוטובוס

The only change is נוסע → נוסעת.

That is very common in Hebrew: with אני, the verb still changes depending on whether the speaker is male or female.

Yes. In modern Hebrew, the present tense is usually built from forms that historically come from a participle.

The dictionary form is לנסוע = to travel / to go by vehicle.

Its present-tense forms are:

• נוסע = masculine singular
• נוסעת = feminine singular
• נוסעים = masculine plural / mixed plural
• נוסעות = feminine plural

So אני נוסע literally has the structure I traveling, but in real Hebrew it simply means I travel / I am traveling.

In the present tense, Hebrew often does include the subject pronoun, because the verb form shows gender and number, but usually not person.

For example:

• נוסע could mean traveling for I or he, depending on context
• נוסעת could mean I or she

So adding אני and היא makes the meaning clear.

In past and future tense, Hebrew often drops the subject more easily because the verb form itself usually shows the person more clearly.

The prefix ל־ usually means to.

So:

• עבודה = work
• לעבודה = to work

In this kind of sentence, לעבודה usually means to work in the sense of to my workplace / to my job.

So אני נוסע לעבודה means I travel to work or I go to work.

The prefix ב־ usually means in / at / on, but with transportation it often corresponds to English by.

So:

• באוטובוס = by bus / on the bus
• ברכבת = by train / on the train

In this sentence, the natural English translation is:

• באוטובוס = by bus
• ברכבת = by train

This is a very common Hebrew pattern:

• במכונית = by car / in a car
• במונית = by taxi / in a taxi
• במטוס = by plane / on a plane

Because נוסע is the natural verb when talking about traveling, especially by some vehicle.

• לנסוע = to travel / to ride / to go by vehicle
• ללכת = to walk, and sometimes more generally to go

Since the sentence specifically mentions bus and train, נוסע / נוסעת is the best choice.

Compare:

• אני הולך לעבודה = I go to work / I walk to work, depending on context
• אני נוסע לעבודה באוטובוס = I go to work by bus

No. Hebrew does not need a separate word like am in this sentence.

In English, you say:

• I am traveling
• She is traveling

In Hebrew, the form נוסע / נוסעת already works as the present-tense verb, so:

• אני נוסע = I am traveling / I travel
• היא נוסעת = she is traveling / she travels

So nothing is missing.

Yes, Hebrew word order is somewhat flexible, though the version in your sentence is very natural and neutral.

The sentence as written is:

אני נוסע לעבודה באוטובוס, אבל היא נוסעת ברכבת.

That order feels like:

• subject
• verb
• destination
• means of transport

You may also hear variations such as:

• אני נוסע באוטובוס לעבודה
• אבל היא ברכבת נוסעת — possible, but more marked and less neutral

So the original sentence is a good standard model.

Yes, in this sentence אבל simply means but.

It connects two contrasting ideas:

• I go to work by bus
• but she goes by train

So the sentence contrasts my way of commuting with her way of commuting.

Punctuation works similarly to English here, so the comma before אבל is natural:

אני נוסע לעבודה באוטובוס, אבל היא נוסעת ברכבת.