What are the forms for the termination of individual employment contracts?

The employment laws in Portugal set out different forms and criteria for the termination of employment contracts:

• Expiration terms listed in the contract
  
• The impossibility to achieve the tasks fixed by the contract
  
• Due to Retirement or disability
  
• Mutual agreement from both parties
  
• Due to dismissal or firing
  
• Termination by the employee 
  
• Termination during the trial period