הוא היה עייף היום כולו.

Hu haya ayef hayom kulo.

A slightly more detailed breakdown:

• הוא = hu
• היה = haya
• עייף = ayef
• היום = hayom
• כולו = kulo

In modern Israeli Hebrew, ע in עייף is usually not strongly pronounced, so the word begins more or less with the vowel sound a.

Because Hebrew often says was + adjective exactly this way.

• היה = was
• עייף = tired

So היה עייף means was tired.

Hebrew does not need a separate special form for was tired. It simply uses the past tense of to be plus the adjective.

This is a very common Hebrew pattern:

• In the present tense, Hebrew usually does not say is/am/are.
• In the past and future, it does use forms of to be.

So:

• הוא עייף = He is tired
• הוא היה עייף = He was tired
• הוא יהיה עייף = He will be tired

That is why היה appears here: the sentence is in the past.

Because עייף is the masculine singular form, and the subject is הוא, which means he.

Hebrew adjectives agree with the person or thing they describe.

So:

• הוא היה עייף = He was tired
• היא הייתה עייפה = She was tired

If the subject changed, the adjective would change too.

Literally, היום כולו is something like the day, all of it or the whole day.

Here:

• היום = the day / today
• כולו = all of it / its entirety

Together, they mean the whole day or all day.

So the sentence means that he was tired throughout the entire day.

כולו agrees with היום.

Since יום is masculine singular, Hebrew uses כולו.

Compare:

• היום כולו = the whole day
• השנה כולה = the whole year
• הלילות כולם = all the nights

So the form changes depending on the gender and number of the noun it refers to.

Both can mean all day.

• כל היום is usually the more common everyday phrasing.
• היום כולו can sound a little more formal, literary, or emphatic.

So:

• הוא היה עייף כל היום = very natural, everyday Hebrew
• הוא היה עייף היום כולו = also correct, with a slightly fuller or more emphatic feel

Because עייף is a predicate adjective, not part of a noun phrase.

Compare:

• הילד העייף = the tired boy
  Here, עייף describes a noun directly, so it takes ה־ when the noun is definite.

• הילד היה עייף = the boy was tired
  Here, עייף comes after היה and functions as the description of the subject, so it does not take ה־.

So in your sentence, עייף stays indefinite-looking even though in English we simply say tired.

Yes, often it can, especially if the subject is already clear from context.

So היה עייף היום כולו can be understood as He was tired the whole day, depending on context.

Hebrew often leaves out subject pronouns because the verb already gives useful information. Here, היה already tells you it is 3rd person masculine singular.

Still, keeping הוא is very normal and can make the sentence clearer.

Not completely, but the given order is neutral and natural:

הוא היה עייף היום כולו

Hebrew can move parts around for emphasis. For example:

• היום כולו הוא היה עייף = He was tired the whole day
• עייף הוא היה היום כולו = possible, but much more marked or literary

For ordinary speech, the original order is a good standard pattern: subject + היה + adjective + time expression