| US spelling | UK spelling/usage | |
|---|---|---|
| or → our | favor behavior | favour behaviour |
| color | colour, but coloration, colorimetry, decolorise, discoloration | |
| tumor | tumour | |
| humor | humour (fluid), but humoral, humorally | |
| er → re | fiber | fibre (but filter) |
| titer | titre | |
| liter | litre | |
| meter | metre (unit) but meter for measuring device. Note also diameter | |
| caliber | calibre | |
| center | centre (except in US addresses and others officially spelled with '… er', e.g. Steno Diabetes Center | |
| l → ll | labeled | labelled |
| signaled | signalled | |
| modeled | modelled | |
| equaled | equalled | |
| f → ph | sulfur | sulphur |
| e → oe | apnea | apnoea |
| diarrhea | diarrhoea | |
| eosophageal | oeosophageal | |
| estrogen | oestrogen | |
| maneuver | manoeuvre | |
| e → ae | endotoxemia | endotoxaemia |
| hyperglycemia | hyperglycaemia | |
| hemoglobin | haemoglobin | |
| ischemia | ischaemia | |
| anesthetised | anaesthetised | |
| etiology | aetiology | |
| uremia | uraemia | |
| pediatric | paediatric (but pedagogic) | |
| log → logue | homolog | homologue |
| catalog | catalogue | |
| analog | analogue | |
| s → c | defense | defence |
| offense | offence | |
| practise | Verb: practise; noun: practice | |
| license | Verb: license; noun: licence | |
| lyz → lys | analyzed | analysed |
| dialyzed | dialysed | |
| catalyzed | catalysed | |
| Miscellaneous | aging | ageing |
| aluminum | aluminium | |
| artifact | artefact | |
| billion | 1000 million | |
| different than | different from | |
| drug store | pharmacy (medicines obtainable on or off prescription)/chemist (incorporates pharmacy but also sells toiletries) | |
| EKG | ECG | |
| fall | autumn | |
| gray | grey | |
| fulfill | fulfil | |
| guinea pig | guinea-pig | |
| leukocyte | leucocyte | |
| mold | mould | |
| operating room | operating theatre | |
| program | programme (except for computer program) | |
| skillfull | skilful | |
| toward | towards |