Through and thru have the same meaning. The only difference between these two words is the spelling. Thru is a common slang used while chatting; people now spell through as thru in order to save them time while typing on social media. However, this is an informal way of spelling the word “through,” as it will not be accepted informal life.
“Drive-thru” is now one of the words that have accepted the use of “Through” is can be used as a preposition, an adverb, or adjective. It means to pass into or to go.
The word through comes from an old English word “Thurh” from the old Saxon word “thru” derived from the old high German “duruh” which comes from a Proto-Indo European base “tere” which means “through or beyond.”
The rise of instant messaging and texting has changes the format in which a lot of words are spelled. The newly accepted form of spelling of many words is shortened and easier to text with the smaller keyboards. An example of that is the word thru. It is a shortened version of the word.
Thru is easier to text and is shorter, but it means the exact something as through, which is to be moving in a time period or in between something. Through is formal and accepted in documents like papers or thesis'. Thru is informal and should only be used in casual conversation.
One thing that you should realize is that through and thru will have the same meaning. The only difference between the two aside from the spelling is when they will be used. Through is the word that will be used by people who would like to use the word formally.
Thru can be used when you are having a normal conversation with friends or when you know that you are just informal. A lot of people say that thru should be avoided because this is not considered to be the proper spelling of the term, but some people still use it, especially in certain situations.
For example, “drive-thru places” instead of “drive-through.” Using it in written form, especially in academic articles, should generally be avoided.