- New Tweets will contain a twitter.created_at field - this will not appear on retweets.
- Retweets will contain a twitter.retweet object - regular Tweets will not.
- Replies will contain a twitter.in_reply_to_*. Retweets of replies will contain a twitter.retweeted.in_reply_to_*
- Mentions will contain a twitter.mentions array, or a twitter.retweet.mentions array if it is a retweet.
Be aware that some of these definitons can overlap - a new Tweet can also be a reply, and in being a reply, it is also a mention.