Meaning of ELEMENTARY in English
el ‧ e ‧ men ‧ ta ‧ ry /ˌeləˈment ə ri◂, ˌelɪˈment ə ri◂/ BrE AmE adjective
1 . simple or basic:
the elementary principles of justice and democracy
You’ve made a very elementary mistake.
2 . [only before noun] concerning the first and easiest part of a subject ⇨ intermediate , advanced :
I’m only familiar with the subject at an elementary level.
I know a little elementary science.
3 . [only before noun] American English relating to elementary school SYN primary British English :
4 . Elementary, my dear Watson. people sometimes use this expression humorously to say how easy something is to solve. Some people think that the phrase comes from the Sherlock Holmes stories by Sir Arthur Conan Doyle. Holmes says this to his friend Watson when explaining how easy it is to understand something about a crime. In fact, the phrase does not appear in the books.
Longman Dictionary of Contemporary English. Longman - Словарь современного английского языка. 2012