lo
/lo/ · A1 · article
neuter definite article used only before nominalized adjectives: the, that which is
From Latin illud (that thing): lo turns an adjective into the ... thing
Latin neuter illud lost its first syllable and became lo. With no neuter nouns left in Spanish, lo only fronts adjectives: lo bueno = the good part, lo importante = what matters. Read lo + adjective as the ... thing.