Consider the following example, where the Chinese noun 苹果 is aligned to six English strings (aligned elements are underlined): (1) a. eat apples <> 吃 苹果 b. eat an apple <> 吃 苹果 c. eat the apple <> 吃 苹果 d. fond of apples <> 喜欢 苹果 e. talk about apples <> 谈论 苹果 f. provide them with apples <> 给 他们 苹果 The English apple and the Chinese 苹果 match in meaning and are both unambiguous.
most of the existing parallel treebanks (Li et al., 2012;Megyesi et al., 2010) do not have phrase alignments.