The Greek word ámmos (ἄμμος) means sand — the fine granular material of seashores and deserts. In Scripture it appears as a metaphor for innumerable multitudes, unstable foundations, and the immensity of God's purposes.
Sand carries two contrasting theological meanings in Scripture. As a measure of abundance, it symbolizes God's staggering promises: Abraham's descendants 'as numerous as the sand' (Genesis 22:17, Romans 9:27), the thoughts of God 'outnumbering the grains of sand' (Psalm 139:18). As a foundation material, it symbolizes instability: the foolish builder who builds on sand sees his house collapse in the storm (Matthew 7:26-27). The same substance is both promise and warning — God's faithfulness is as vast as every grain of sand, but human life built apart from His word is as unstable as sand under rising water.