Please find the below trigger ...getting below error " Initial term of field expression must be a concrete SObject: LIST<Account>"

Could you please let me know what is this error ?

trigger AccountDuplicate on Account (before insert, before update)
{
    for(Account a:Trigger.new)
    {
        List<Account> acc =[select id, Name from Account where Name=:a.Name];
        if(acc.size()>0)
        {
        acc.Name.addError('You Cannot Create the Duplicate Account');
        }
    }
}

Please find the below trigger ...getting below error " Initial term of field expression must be a concrete SObject: LIST<Account>"

Could you please let me know what is this error ?

trigger AccountDuplicate on Account (before insert, before update)
{
    for(Account a:Trigger.new)
    {
        List<Account> acc =[select id, Name from Account where Name=:a.Name];
        if(acc.size()>0)
        {
        acc.Name.addError('You Cannot Create the Duplicate Account');
        }
    }
}