Academic expulsion, or even probation, isn't something you want on your record. If you have some valid reason why you were unable to maintain a required grade point average, most universities will allow you to appeal the punishment. A formal letter of appeal is a major component of that appeal. The letter must look professional. Type it and check it for spelling and grammar.
Start with "To whom this may concern: or Attention: Board of appeal." The financial office may be able to tell you the name of the person to address.
Include your name and social security number in the body of the letter.
Explain in detail any personal issues you had during the semester. If you were caring for a sick parent or working through some other major life event, explain it here in brief but direct terms. You must also explain what you have done to rectify the problem so it will not bother you in the upcoming semester.
Follow the explanation with a short paragraph on what you hope to accomplish with your degree.
Thank the committee for their time and any consideration they can give you, then sign the letter. Include your social security number again under the signature. Add a mailing address and contact number.