So , a person who has trouble understanding anything ( hardly understands ) call - slow or dim , however, it is worth remembering that they are usually soften putting ahead a bit , or rather.
Her husband's a bit dim.
My students were rather slow.
Of students who study with things are not going , they will say that he struggle
My daughter struggles with maths. She's struggling at school.
The following statement has more offensive and is used to say "a person without a hint of intelligence » - a vacuous expression (vacuous [ 'vækjuəs] - meaningless , empty