Correct spelling for the English word "plainlier" is [plˈe͡ɪnliə], [plˈeɪnliə], [p_l_ˈeɪ_n_l_i__ə] (IPA phonetic alphabet).
The word "plainlier" is derived from the combination of two primary elements: "plain" and the suffix "-er".
1. "Plain" is derived from the Old French word "plein" (meaning "full, abundant, complete"), which can be traced back to the Latin word "plēnus". Over time, "plain" came to mean "clear, evident, simple" in English.
2. The suffix "-er" is a common suffix in English that can serve various functions, including forming the comparative degree of an adjective or adverb. In this case, "-er" is added to "plain" to form the comparative adverb "plainlier", meaning "in a plainer or clearer manner".
Therefore, the etymology of "plainlier" is a combination of the Old French "plein" and the English suffix "-er".