The idiom "all along" means that something was true or existed for the entire time, even though it may not have been obvious or acknowledged at first.
For example, if someone says "I knew all along that he was lying," it means that they had a feeling or suspicion that the person was lying from the beginning, even if they didn't have concrete evidence at the time.
Another example could be "The answer was right in front of me all along," meaning that the solution to a problem was obvious and present the whole time, but it took some time to realize it.
You can use this idiom in situations where you want to emphasize that something was always true or present, even if it wasn't immediately recognized. It can also be used to express a sense of frustration or regret for not realizing something sooner.
• All along, she suspected that her friend was lying.
• I knew the answer to the question all along.
• All along, I had a feeling that this project was going to be successful.
• He had been planning his revenge all along.
• All along, the company knew that their product was faulty but didn't take any action.
• She had been deceiving her colleagues all along and finally got caught.