guideline guideline /ˈgaɪdˌlaɪn/

noun

1. A rule or principle that provides guidance to appropriate behavior  ( guideline , rule of thumb , guidepost )
   a rule or principle that provides guidance to appropriate behavior
   
2. A detailed plan or explanation to guide you in setting standards or determining a course of action  ( guideline , road map )
   a detailed plan or explanation to guide you in setting standards or determining a course of action
    The president said he had a road map for normalizing relations with Vietnam
   the president said he had a road map for normalizing relations with Vietnam
   
3. A light line that is used in lettering to help align the letters  ( guideline )
   a light line that is used in lettering to help align the letters