Rule is one of the 400 words for general things. The root-sense of the word is règle in French; Regel or Vorschrift in German. It is sometimes necessary to "make new rules for the society."

As a rule is a fixed word-group used frequently.

Another sense of this word, an expansion from the root, is straight-edged instrument for measuring. The control of the instrument, in addition, is a rule. It is règne in French. Because it is used for making lines, it is Lineal in German. Another German word with the same sense is Zollstock.

Ruler is another name for this instrument.

Ruler is sometimes person with a political power, taking control of a government, nation or country. It is souverain in French; Herrscher in German. Act of ruling a country, in addition, is rule. It is Herrschaft in German. The years when King John was ruler of England were the times "under the rule of John." A good ruler is someone ruling a country well.

Ruling lines may be stronger than guidelines.

Ruled is another possible form of this word, based on Ogden's rules (The Basic Words).

Words like règle and Regel probably have the common roots with the English word regular.

Rules, of Basic English, from Ogden's word list:

Additions of "s" to things when there is more than one. Forms ending in "er," "ing," "ed" from 300 names of things. "Ly" forms from qualities. Degree with "more" and "most." Questions by change of order and "do." Form-changes in names of acts, and "that," "this," "I," "he," "you," "who," as in normal English. Measures numbers days, months and the international words in English froms.  ¶ 15:14