1. A word recognition system for identifying a spoken word represented by an analog speech signal, said word recognition system comprising: signal processing means for receiving an analog input speech signal and for producing feature vectors from the input speech signal to provide a sequence of feature vectors at predetermined speech frame intervals as an output therefrom; memory means storing a plurality of reference templates of digital speech data respectively representative of individual words and comprising the vocabulary of the word recognition system, each of said reference templates being defined by a predetermined plurality of reference vectors arranged in a predetermined sequence and comprising an acoustic description of an individual word in a time-ordered sequence, each of said reference templates being further defined by at least one mask vector respectively associated with each said sequence of reference templates being further defined by at least one mask vector respectively associated with each said sequence of reference vectors and being indicative of the significance of portions of the reference vector sequence association therewith in establishing the identity of the word represented by the reference template of which said at least one mask vector is a component; means operably associated with said signal processing means for comparing each feature vector of said input speech signal with the corresponding reference vectors of each of said reference templates to provide a distance measure with respect to each of the feature vectors and the predetermined reference vector sequences defining acoustic descriptions of the respective words included in the vocabulary of the word recognition system, said comparing means being responsive to the status of the respective mask vectors comprising components of said plurality of reference templates to ignore elements of reference vectors included in respective reference templates which are indicated by the associated mask vector to be insignificant so as to provide said distance measure based upon significant elements of the reference vectors as included in the predetermined reference vector sequences; and word recognizing means operably associated with said comparing means for determining which one of the plurality of the reference templates is the closest match to said input speech signal based upon the distance measures of said reference vector sequences and successively received feature vectors corresponding to respective speech frames.