(used to introduce a logical conclusion) from that fact or reason or as a result
"therefore X must be true"
"the eggs were fresh and hence satisfactory"
"we were young and thence optimistic"
"it is late and thus we must go"
"the witness is biased and so cannot be trusted"
as a consequence
"he had good reason to be grateful for the opportunities which they had made available to him and which consequently led to the good position he now held"
For that or this purpose, referring to something previously stated.
"We installed extra insulation in the attic; therefore, our heating bills have dropped significantly."
In plain English: Therefore means that something happens as a direct result of what came before.
"It started raining heavily, therefore we decided to stay inside."
Usage: Use therefore at the beginning of a sentence with a comma following it when introducing a conclusion based on previous information. Avoid placing it in the middle of a clause unless you add commas before and after for clarity.
Therefore comes from Middle English, originally combining "there" and "for" to mean "for that reason." Over time, speakers reinterpreted the word as "there" plus "fore," shifting its literal sense to "forward from that place."