 In discussing Spanish, Martínez Celdrán suggests setting up a third category of "spirant approximant", contrasting both with semivowel approximants and with fricatives.Though the spirant approximant is more constricted (having a lower F2 amplitude), longer, and unspecified for rounding ("viuda" 'widow' vs. "ayuda" 'help'), the distributional overlap is limited.The spirant approximant can only appear in the syllable onset (including word-initially, where the semivowel never appears).