Here is a rundown on the example of emails:
- Interception or Snooping or Sniffing
An attacker intercepts the unencrypted traffic of an email server to record and modify the content of sent and received emails. (Your ISP, router or network administrator are all able to sniff/intercept the unencrypted traffic that they process.)
An attacker crafts an email with a forged sender address to appear as if it comes from your boss and asks you for a password. This is aptly called email spoofing.
Falsification refers to spoofing. In a spoofing attack you falsify ("forge") data.
An attacker gains access to your mail account and sends rude messages to your boss. You probably can't repudiate (deny) having sent these messages easily because the system doesn't keep track of the IPs that logged in to your account.
You might want to have a look at STRIDE, one of the most common models to classify security threats. It distinguishes Spoofing, Tampering, Repudiation, Information disclosure, Denial of service and Elevation of privilege. This classification might be a little more thorough than your proposed list.
Microsoft has a good overview on threats and countermeasures that includes STRIDE.