Since
  يأتي بعدها بداية فترة زمنية نعرف  أولها ولا نعرف متي تنتهي 
  فنقول مثلا 
  since 8 o'clock
  since Monday
  since 12 May
  since April
  since 1977
  since Christmas
  since lunchtime
  since they were at school
  
  وإليكم بعض الأمثلة 
  She has been in hospital since  Monday
  I have been waiting since 8  o'clock..
  They have known each other since  they were at school
For
  يأتي بعدها فترة زمنية محددة لا نعرف  متي بدأت ولا متي إنتهت 
  فنقول مثلا 
  
    
  
 
  
  
  
  
  
  
  
  
  
  
for two hours
    for 20 minutes
    for five days
    for six months ..
    for a week
    for 50 years
    for a long time
    for ages
    
    ونذكر أيضا بعض الأمثلة  
    She has been married for ten years
    I haven't seen her for three months 
    We have known each other for ages
    I 've been waiting for the last half  hour
    
    
و أود أن أوضح نقطة أخري هامة وهي الفرق  بين 
    gone to   -   been to
فعندما نقول مثلا 
    He has gone to Spain
  هنا هذه الجملة تعني 
  أنه الأن في أسبانيا أو في طريقه إلي  هناك
    ولكن عندما نقول 
  He has been to Spain
فالجملة هنا تعني 
  أنه الأن قد عاد من أسبانيا ولم يعد  هناك