Formal expression for "talking about something unrelated" [closed]

What are some words or phrases that can be used when a person is discussing a particular subject with a group of people and unintentionally she/he talks about something unrelated? I need a formal expression.

Solution 1:

Here are a few ways of expressing that, from casual to more formal:

• Going off-topic
• Getting off track
• Rambling or not getting to the point
• Losing focus
• Digressing
• Tangential to the discussion
• Not relevant to the topic at hand
• Diverting the conversation
• Subject is not pertinent to the conversation

Solution 2:

I'm fond of going off-topic. You could also say that they are going off on a tangent or speaking tangentially.

Solution 3:

The short answer is: "digress". It means to go off-topic.