היא חכמה יותר ממנו.

Because in present-tense Hebrew, the verb to be is usually not said.

So:

• היא חכמה = she is smart
• not literally with a separate word for is

This is very normal in Hebrew. In the past or future, Hebrew does use forms of היה.

Because the subject is היא (she), which is feminine singular.

Hebrew adjectives must agree with the noun or pronoun they describe in:

• gender
• number

So:

• חכם = masculine singular
• חכמה = feminine singular

Since the sentence starts with היא, the adjective has to be חכמה.

יותר means more.

Hebrew usually forms comparisons with:

• adjective + יותר + מ־...
• literally something like smart more than...

So חכמה יותר means smarter.

Unlike English, Hebrew does not usually add an -er ending to the adjective. Instead, it uses יותר.

Examples:

• גדול יותר = bigger
• מהיר יותר = faster
• יפה יותר = more beautiful / prettier

Because after a comparison in Hebrew, you normally use the preposition מ־ / מן to mean than.

So Hebrew does not say:

• יותר הוא

It says:

• יותר ממנו = more than him

Here, ממנו is the prepositional form meaning from him / than him, depending on context.

This is similar to how English needs than him rather than just he in everyday speech.

Yes — the same form can mean from him, but in a comparative sentence it is understood as than him.

So:

• לקחתי ממנו ספר = I took a book from him
• היא חכמה יותר ממנו = she is smarter than him

The meaning comes from the context.

It is the preposition מן / מ־ plus the pronoun he/him.

With pronouns, Hebrew often uses special combined forms:

• ממני = from me / than me
• ממך = from you / than you
• ממנו = from him / than him
• ממנה = from her / than her

So ממנו is not random; it is just the regular fused form for from/than him.

Yes. That is also natural Hebrew.

Both of these are used:

• היא חכמה יותר ממנו
• היא יותר חכמה ממנו

Both mean the same thing.

Very roughly:

• חכמה יותר can sound a bit more neutral or standard
• יותר חכמה is also very common, especially in speech

As a learner, you should recognize both.

You change both the adjective agreement and the comparison pronoun if needed.

Examples:

• הוא חכם יותר ממנה = he is smarter than her
• הוא חכם יותר ממנו = he is smarter than him
• היא חכמה יותר ממנה = she is smarter than her

Main changes:

• היא → הוא if the subject is male
• חכמה → חכם for masculine singular
• ממנו ↔ ממנה depending on who is being compared

A rough pronunciation is:

hi khakhamá yotér miménu

A few notes:

• היא = hi
• ח is a throaty sound, like the ch in German Bach or Scottish loch
• חכמה here is roughly kha-kha-MA
• יותר is roughly yo-TER
• ממנו is roughly mi-ME-nu

If you cannot make the ח sound yet, using a plain h/k-like approximation is common for beginners.

Usually, with a simple noun or pronoun like him, ממנו is the normal choice.

So this sentence is best as:

• היא חכמה יותר ממנו

מאשר is more often used before a full clause, for example:

• היא חכמה יותר מאשר חשבתי = she is smarter than I thought

You may sometimes hear מאשר in other comparisons too, but for this sentence, ממנו is the most natural form.