This study focussed on the effect of grammar of Iwaidja, an indigenous Australian language, on mathematical conceptualisation. It investigated route description in Iwaidja. Spatial concepts such as direction, height and movement in relation to another object are briefly described using examples. Differences between English and Iwaidja are used to illustrate the some of the impact of grammar on mathematical conceptualisation. The implications are discussed in terms of how understanding these grammatical features can help teachers, especially when children are not fluent in the language of instruction, as well as providing keys to cross-linguistic investigations of mathematical cognition.