368. When the prefix in, en, or un is added to words beginning with n (as in nerve-innerve, noble-ennoble, necessary-unnecessary), or the equivalent prefix il, im, or ir, to words beginning with /, m, or r, respectively (as in legal-illegal, moderate-immoderate, regular-irregular), the outlines of the derivatives (innerve, ennoble, unnecessary, illegal, immoderate, irregular, etc.) are distinguished from those of the primitives {nerve, noble, necessary, legal, etc.) by repeating the sign of the first consonant of the primitives.

369. Sometimes the rule at 104, for the use of downstrokes and upstrokes at the beginning of outlines, as affected by the absence or presence of an initial vowel, may be applied, thereby obviating the necessity of duplicating the first consonant; as in the outlines of irrigation, illustration, illustrate, irrelevant, irreligious, etc.

Reading Exercise.

Writing Exercise.

370.    Unnatural, unnavigable, unnecessary, unnoticed, illegal, illegible, immemorial, immoderate, immoral (-M-Rl), immortal (-Mrt-L), irreverent, irremediable, irrefutable, irregular, removable, irremovable [irremediable], irrepressible, irresistible, irrespective, irrevocable. (369) Irruption, irreligious (R-L-), illumination.