This is the 137th most frequent Chinese word.
所以
"所以" means "therefore" or "so."
Here, '所以' links the observation 'the weather has turned cold' with the resulting action 'we decided to have dinner at home.' It emphasizes the logical connection between the observation and the decision.
天气变冷了，所以我们决定今天在家吃晚饭。
The weather has turned cold, so we decided to have dinner at home today.
In this example, '所以' shows the logical consequent 'please adjust your plans' arising from the premise 'the meeting will be postponed until tomorrow.' It implicitly carries the meaning of 'therefore.'
会议将延迟到明天，所以请大家调整计划。
The meeting will be postponed until tomorrow, so please adjust your plans.
In this sentence, '所以' is used to indicate the resultant conclusion 'his grades are excellent' due to the cause 'he studies very hard.' It connects the cause and effect relationship between two clauses.