A three-dimensional alignment is a triplet of symbols (σ : For example, the words meaning "9" in Finnish, Estonian and Mordva, can be aligned simultaneously as: In 3-D alignment, the input data contains all examples where words in at least two languages are present 5i.e., a word may be missing from one of the languages, (which allows us to utilize more of the data).
we have two types of examples: complete-where all three words present (as "9" above), and incompletecontaining words in only two languages.