We are familiar with the image of falling leaves and the poignancy that creates. Poems are full of that image. But cummings is illustrating that poignancy in several ways. First, the words themselves: "a leaf falls loneliness" or "loneliness a leaf falls." It doesn't work well to read it that way does it? Second, in the long, lean lines; the downward fluidity of the poem as a whole created with the whole line, and the lines of the letters. Third, those parentheses! Parentheses are inherently exclusive. cummings illustrates loneliness by alienating that word from the rest of the poem. And fourth, although this list is by no means comprehensive, the title. l(a. Alienation and loneliness is inherent in the separation, the boundary, between those two letters.