The difference in meaning of "Due"

Question

It might be a duplicate, but I can't find one with my short searching.

I found the two sentences with different meaning of "due"

1. I had to abandon my project due to a lack of government funding.
2. He is due to start school in this March.

As a foreigner, I learned the first 'due' means, with 'due to', 'because of', or kind of meaning cause and effect (exactly, effect and cause). But, I think second 'due', in most other cases, means 'the necessity of doing something' or 'it plans to'.

I can't understand why 1st meaning comes from 2nd meaning. Is it just a word with multiple meaning? Or, does 'due' have something special links between them, related with a preposition 'to'?

Thanks.

Answer 1

Due is a word with multiple meanings

The basic meaning is "owing" and is related to debt. A derived meaning is "expected" (since we expect a debt to be paid). This meaning is used in the last example.

He is due [to start school] [this March]

Note that "to" is not a preposition here, it is the particle in the infinitive verb "to start".

Another meaning of due is in a preposition phrase "due to" which means "because of". The connection is the idea payment is "because of" a debt. We also say "owing to", with roughly the same meaning. And this is the sense used in the first example sentence.

The meaning "due to" = "because of" is actually quite recent, dating from about 1900, and is not the main meaning.