HOW TO READ THE DICTIONARY
As you know very well，dictionaries are reference books
— books not for continuous reading but for occasional consulting. But I would here advise you to read，from time to time, a page or two in The Concise Oxford Dictionary or The Pocket Oxford Dictionary. Each of these two dictionaries explains and illustrates fully and clearly the common words that are met with every day but are entangled with other words in so many connexions that the idiomatic use and right understanding of them are far from easy. For example，“on” seems plain and simple enough；but few Chinese students can always use and understand it correctly. When I advise you to read the dictionary，I mean such common words as the prepositions，the conjunctions，the pronouns，and simple verbs and nouns like “get” and “put”，“head” and “way”.
Now let us read the preposition “above” in The Pocket Oxford Dictionary：
“Over，higher than，up stream from，projecting from，north of，earlier in history than，（the roof a. me；head a. water；not traced a. third century）；of higher rank，position，importance，& c.，than （a. all）；out of reach of （a. suspicion）；too good & c. for （is a. meanness；a. one’s station；a. oneself，carried away by high spirits，self-esteem，& c.）.”
A few points need to be noticed. The letter “a.” here stands for “above”. Before “third century” and before “reach of” the article “the” is understood. “Oneself” stands for “himself”，“herself”，etc.
Let us also read a small part of the verb “call” in the same dictionary：
“Speak in tone meant to reach distant hearer （to person），utter a summons or （esp. of bird，trumpet，& c.） a signal，pay brief visit at place，on person.”
From “（to person）” we learn that we may say “I called to her” and “They are calling to their friend”. From “pay brief visit at place，on person”，we learn that we may say “I called at the office” and “I called on him”，but not “I called on the office” and “I called at him”.