What part of speech is “due-to”

'due to' is a compound preposition made up of two parts 'due' and 'to'. It functions as a means of introducing a clause which states the cause, reason, or basis of something. Examples include 'due to the weather', 'due to a prior commitment', or 'due to unforeseen events'. In terms of usage, it is nearly identical to 'because of' or 'on account of'.

1. She was promoted due to her hard work.

2. He changed his plans due to the bad weather.

3. I was unable to attend due to a prior commitment.

the phrase 'due to' should not be followed by a verb. For example, 'due to run' is incorrect; instead, use 'due to the fact that (noun phrase) was running'.