Adjectives in English do not become plural if they are followed by plural nouns. The only exception is demonstrative adjectives. Occasionally, a plural noun will be made into an adjective but this is not because of agreement with the noun but because of what the noun refers to, e.g. The Twin Tours disaster led to the deaths of many people.
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A colon points forward to what follows. It is commonly used before a list. It is also appropriately used to introduce a quotation.
Semi-colons (;) have two common functions. First, a semi-colon is like a weak full-stop and separates two closely related sentences, e.g. It is raining heavily; we can’t go out.
Second, a semi-colon is used in a list instead of a comma where one or more of the items contains a comma, e.g.