Learn Dutch: De baas zal het vandaag wel erg druk hebben. - The boss is probably very busy today.

While zullen is often used for the future tense ("will"), it is also frequently used to express an assumption or strong probability. In this sentence, zal implies that you are guessing or assuming the boss is busy right now based on what you know.

What is the purpose of the word wel in this sentence?

Wel is a modal particle (a small word that changes the tone of a sentence). When paired with zullen, it reinforces that the statement is a guess or expectation. The combination zal wel is very common and translates smoothly to "will probably" or "must be".

Why is the word het used here, and why the verb hebben instead of zijn (to be)?

In Dutch, you don't usually describe a person's schedule as being busy using the verb zijn (to be). Instead, you use the fixed expression het druk hebben (literally: to have it busy). If you say de baas is druk, it sounds more like the boss is acting physically hyperactive, or you are describing a busy place (like a street).

Why does the verb hebben come at the very end of the sentence?

This is a standard Dutch word order rule. In a main clause with a modal verb, the modal verb (zal) takes the second position, and the main infinitive verb (hebben) gets pushed all the way to the end of the sentence.