I tell a lie

I tell a lie means: I am mistaken; I thought that what I said (or wrote) was true, but I have just realised that it is not.. There is no real cause for parental concern; it is descriptive vocabulary rather than risky behaviour. If your teen uses it, context will usually make the intent clear. A short, curious question about where they heard it is usually all that is needed to know whether to follow up.

I tell a lie means: I am mistaken; I thought that what I said (or wrote) was true, but I have just realised that it is not.. Register: neutral, standard English. A common learner mistake is using the word in a register it does not fit, or assuming a single global meaning; native speakers immediately notice when slang appears in formal contexts, so always check the surrounding register before producing it yourself.