The　reduced　elastic　modulus　Er　and　indentation　hardness　HIT　of　various　brittle　solids　including　ceramics,　semiconductors,　glasses,　single　crystals,　and　laser　material　were　evaluated　using　nanoindentation.　Various　analysis　procedures　were　compared　such　as　Oliver　&　Pharr　and　nominal　hardness-based　methods,　which　require　area　function　of　the　indenter,　and　other　methods　based　on　energy,　displacement,　contact　depth,　and　contact　stiffness,　which　do　not　require　calibration　of　the　indenter.　Elastic　recovery　of　the　imprint　by　the　Knoop　indenter　was　also　utilized　to　evaluate　elastic　moduli　of　brittle　solids.　Expressions　relating　HIT/Er　and　dimensionless　nanoindentation　variables　(e.g.,　the　ratio　of　elastic　work　over　total　work　and　the　ratio　of　permanent　displacement　over　maximum　displacement)　are　found　to　be　nonlinear　rather　than　linear　for　brittle　solids.　The　plastic　hardness　Hp　of　brittle　solids　(except　traditional　glasses)　extracted　based　on　Er　is　found　to　be　proportional　to　ErHIT.　(Figure　presented.)　©　The　Chinese　Society　of　Theoretical　and　Applied　Mechanics　and　Springer-Verlag　GmbH　Germany,　part　of　Springer　Nature　2024.