Hello as : is used to describe a similarity to what is mentioned before it , usually in the form of ( as .....as ) He speaks english as good as his friend. since : means "from that time ,from then till now " He lives in Indonesia since 2 years. He got this job since 1 month . because : gives a reason for the statement mentioned before it . He can't come ,because he is busy due to : gives also reason for the statement before ,but the sentence structure is different then when using "because". He can't come due to his busy schedule , or his busyness . I hope that is clear enough :)

We use "as, since, because ,and due to" to show cause and effect relationships.