| Subject | English | German |
| coal., met. | Hardness Index | Haertefaktor |
| coal., met. | Hardness Index | Hardness Factor |
| IT, coal., met. | Hardness-Index ASTM | Abrieb |
| IT, coal., met. | Hardness-Index ASTM | Abriebfestigkeitswert |
| IT, coal., met. | Hardness-Index ASTM | Abriebfestigkeit |
| IT, coal., met. | Hardness-Index ASTM | Abriebwert |
| mater.sc. | index of hardness | Härtegrad |
| mater.sc. | index of hardness | Härtezahl |