- arch form
- arch limp
- arch pressure
- arch truss
- archaeologist
- arched floor
- arched support
- archeozoic
- architectural concrete
- architectural ensemble
- architectural light
- architectural order
- archive attribute
- archived file
- archiver
- archway
- archy
- arcing horn
- arcose
- arcticization
- area code
- area meter
- areal geology
- areola
- argilization
- argillite
- argillous
- argon
- argue
- argument separator
- arithmetic mean
- arithmetic object
- arithmetic point
- arithmetic series
- arithmetic statement
- arithmetic unit
- arithmetical instruction
- arithmometer
- arm crank
- armature core
- armature winding
- arming
- armored
- armored lining
- armoring tape
- armour plate
- armoured cable
- aroma
- aromatic
- array descriptor
- array processor
- arrestor
- arris gutter
- arrow cursor
- arteria innominata
- arterial dragline
- arterial road
- artesian water
- artesian well
- articulated coupling
- articulated system
- artificial ageing
- artificial channel
- artificial constraint
- artificial crown
- artificial ice
- artificial lake
- artificial light
- artificial sample
- artificial source
- artificial voice
- as
- asbestos
- asbestos fiber
- asbestos sheathing
- ascending
- ascending grade
- ascending order
- ascertain
- ash rain
- ash rock
- ash-pan
- ash-stand
- ashlar
- ashlar vault
- aspect
- asperity
- aspersion
- asphalt emulsion
- asphalt felt
- asphalt pavement
- asphalt road
- asphalted felt
- asphaltic petroleum
- asphaltic rock
- asphyxiate
- aspirant tube
- aspiration cap
- aspirator
- assemblage