If record projectors commute with an apparatus-environment interaction, their populations are preserved while the corresponding environmental states can become distinguishable. Their conditional environment overlap then suppresses interference in the apparatus reduced density matrix. A nondegenerate record coupling can thereby select robust sectors; commutation alone does not select a unique basis in a degenerate or trivial interaction.^[ref]

The characteristic relation between imposed reactor reactivity and exponential growth or decay rates in a point kinetics model. Several kinetic modes can coexist; the late-time behaviour is determined by the mode with greatest real growth rate that is actually excited.

A timescale-separation approximation that eliminates the rapidly adjusting neutron amplitude in favour of the slower delayed neutron precursor reservoir. It describes behaviour after the short prompt transient and need not resolve the initial adjustment.

The effective time associated with successive prompt fission generations in a specified point kinetics model. It is distinct from a macroscopic population growth period, which also depends on reactor reactivity and delayed neutrons.

A molecular point group with identity, one twofold axis, and two mirror planes containing that axis. With the twofold axis along $z$, its one-dimensional irreducible representations have Cartesian bases $z\sim A_1$, $x\sim B_1$, and $y\sim B_2$. For formaldehyde in the $xz$ plane, the vibrational representation is $3A_1+2B_1+B_2$.

A molecular point group containing identity, three mutually perpendicular twofold rotations, inversion, and three mirror reflections. In the conventional axis labelling, $z\sim B_{1u}$, $y\sim B_{2u}$ and $x\sim B_{3u}$; $yz\sim B_{3g}$ and $xz\sim B_{2g}$. The symmetry of a perpendicular atomic $p$ orbital includes its sign reversal when an operation reverses its axis, in addition to any permutation of atomic centres.

The spatial symmetry of a fixed molecular geometry. Its point group acts on atomic positions, orbitals and vibrational coordinates; these actions need not have the same group representation.

A physical property tensor must be invariant under every symmetry operation of the material's point group. For a polar rank-$r$ tensor, $T_{i_1\dots i_r}=R_{i_1{j}_1}\cdots R_{i_r{j}_r}{T}_{j_1\dots j_r}$. Taking $R=-I$ proves that an odd-rank polar tensor vanishes in a centrosymmetric material. A susceptibility of order $n$ has rank $n+1$, so local bulk even-order electric-dipole response is forbidden there. The name refers to Franz Ernst Neumann.

A vacancy and a displaced atom occupying an interstitial position. Recombination restores the occupied lattice site; spatial separation or trapping can allow the defects to survive.

An unoccupied site in an otherwise specified crystal structure. Equilibrium vacancies and an irradiation-driven vacancy supersaturation have different origins.

An extra atom of the host material accommodated outside the ordinary lattice-site inventory. It can migrate, recombine with a vacancy, or join a cluster.

A missing carbon-atom inventory in graphene. Local reconstruction changes the nearby ring pattern and electronic states; irradiation and subsequent annealing can change the reconstruction.

Conducting tissue carrying water and dissolved materials through a vascular plant. Its anatomy and vulnerability to water stress affect plant stature, growth and survival.

Conducting tissue transporting organic compounds and other materials between source and sink regions of a vascular plant.

A pore with associated guard cells in the plant surface. Distribution and function differ among life-cycle stages and lineages; a liverwort air pore is not an equivalent regulated structure.

A surface barrier that limits water exchange with the environment. Its development helps regulate drying, but varies between gametophytes, sporophytes and plant organs.

A region maintaining cells that support continued plant growth and organ production. Floral reproductive development coordinates organ identity with changes in the activity and termination of its meristem.

Circadian clock ASSOCIATED 1 is a morning-associated transcription factor in the Arabidopsis thaliana plant circadian clock. Its interaction with LHY and TOC1 helps relate changing gene expression to the timing of the circadian rhythm.^[ref]

LATE ELONGATED HYPOCOTYL, a morning-associated transcriptional regulator in the Arabidopsis circadian network.

TIMING OF CAB EXPRESSION 1, also called PRR1, an evening-associated transcriptional regulator in the Arabidopsis circadian network.