Fixed word order is one out of many ways to ease the processing of sentence semantics and reducing ambiguity. One method of making the speech stream less open to ambiguity (complete removal of ambiguity is probably impossible) is a fixed order of arguments and other sentence constituents. This works because speech is inherently linear. Another method is to label the constituents in some way, for example with case marking, agreement, or another marker. Fixed word order reduces expressiveness but added marking increases information load in the speech stream, and for these reasons strict word order seldom occurs together with strict morphological marking, one counter-example being Persian.