Skip to content

Main Navigation

Biology Online Logo
  • Dictionary
  • Articles
  • Tutorials




Biology Dictionary: R

Search or browse the dictionary for the definition of biology terms starting with the letter “R”.

  • Featured Terms
  • All Terms
  • Popular Terms
  • Aa
  • Bb
  • Cc
  • Dd
  • Ee
  • Ff
  • Gg
  • Hh
  • Ii
  • Jj
  • Kk
  • Ll
  • Mm
  • Nn
  • Oo
  • Pp
  • Qq
  • Rr
  • Ss
  • Tt
  • Uu
  • Vv
  • Ww
  • Xx
  • Yy
  • Zz
Dictionary > R
AllC

R

  • R factor
  • R loop
  • Rac
  • Race
  • Racemose
  • Rachischisis
  • Rad
  • Radial immunodiffusion
  • Radial symmetry
  • Radiata
  • Radiate
  • Radiation
  • Radiation biophysics
  • Radical
  • Radioactive
  • Radioactive atom
  • Radioactive decay
  • Radiodensity
  • Radix ventralis
  • Raffinose
  • Raillietina
  • Railroad nystagmus
  • Raisins
  • Ramenta
  • Rami
  • Ranal
  • Random allocation
  • Range
  • Ranikhet disease
  • Rare species
  • Ras
  • Rayleigh criterion
  • Rb
  • RDNA
  • Reactants
  • Reaction center
  • Reaction centre
  • Reactive oxygen species
  • Reading frame
  • Reaginic antibody
  • Realized niche
  • Reannealing
  • Rebound phenomenon
  • Recalcitrant
  • Recapitulation theory
  • Receiver cell
  • Recent single-origin hypothesis
  • Receptaculum chyli
  • Receptor
  • Recess
  • Recessive
  • Recessive trait
  • Recombinant DNA
  • Recombination
  • Recombination DNA repair
  • Recon
  • Reconstitution
  • Recruitment
  • Red algae
  • Red blood cell
  • Red drop effect
  • Redia
  • Redox reaction
  • Reduced eye
  • Reduced penetrance
  • Reducing enzyme
  • Reducing sugar
  • Reductant
  • Reductase
  • Reduction
  • Reduction Division
  • Reduction en masse
  • Redundancy Hypothesis
  • Rees-ecker fluid
  • Reflection
  • Reflex
  • Reflex arc
  • Refractile
  • Refractory Period
  • Refuse disposal
  • Regeneration
  • Regio inguinalis
  • Regio lumbalis
  • Regio mentalis
  • Regional anatomy
  • Regional continuity model
  • Regulation
  • Regulator
  • Regulatory gene
  • Regurgitation
  • Reins
  • Relative fitness
  • Relax
  • Relaxed dna
  • Relaxed plasmid
  • Relay neuron
  • Release phenomenon
  • Reliability coefficient
  • Remedies
  • Remission
  • Remove
  • Renal column
  • Renal cortex
  • Renal medulla
  • Renal pyramid
  • Renaturation
  • Renewable resource
  • Rennase
  • Rennin
  • Renogastric
  • Repeated sequences
  • Repellent
  • Repetitive DNA
  • Replacement
  • Replacement bone
  • Replacement model
  • Replica plating
  • Replicase
  • Replicate
  • Replication
  • Repolarization
  • Repression-sensitization
  • Repressor protein
  • Reproduction
  • Reproductive adaptation
  • Reproductive Cell
  • Reproductive isolation
  • Reproductive system
  • Reptiles
  • Reserves
  • Reservoir
  • Reservoir host
  • Residual air
  • Residual volume
  • Residue
  • Resin
  • Resistance
  • Resistance factor
  • Resolvase
  • Resorption
  • Resorption lacunae
  • Resources
  • Respiration
  • Respiration rate
  • Respiratory metabolism
  • Respiratory substrate
  • Respiratory system
  • Respirometer
  • Respondent conditioning
  • Response
  • Rest bite
  • Resting cells
  • Resting potential
  • Resting tidal volume
  • Restriction enzyme
  • Restriction fragments
  • Restriction point
  • Rests of serres
  • Resuscitation
  • Retard
  • Rete testis
  • Retention
  • Reticul-
  • Reticular activating system
  • Reticular connective tissue
  • Reticular fiber
  • Reticulated
  • Reticuloendothelial system
  • Retina
  • Retrograde
  • Retrotransposon
  • Retrovirus
  • Rev
  • Reverberating circuit
  • Reverse banding
  • Reverse passive agglutination
  • Reverse transcription
  • Revertant
  • Revolution
  • Rh factor
  • Rheotaxis
  • Rhinalgia
  • Rhinarium
  • Rhizobium leguminosarum
  • Rhizoids
  • Rhizome
  • Rhizophora
  • Rhizopoda
  • Rhodopsin
  • Rib
  • Ribonuclease
  • Ribonucleic acid
  • Ribonucleoside
  • Ribonucleotide
  • Ribose
  • Ribosomal DNA
  • Ribosomal ribonucleic acid
  • Ribosome
  • Ribozyme
  • Rice
  • Right fibrous trigone
  • Right sagittal fissure
  • Rigidity
  • Rigor
  • Ring test
  • Ripe
  • Rivet Hypothesis
  • Rmv
  • RNA virus
  • RNA-dependent DNA polymerase
  • Rod
  • Roller
  • Rollers nucleus
  • Rolling circle mechanism
  • Roof of mouth
  • Room temperature
  • Root
  • Root cap
  • Root cutting
  • Root Hair
  • Root nodules
  • Root System
  • Rose
  • Rosette formation
  • Rostrum
  • Rostrum sphenoidale
  • Rotary joint
  • Rotatoria
  • Rough endoplasmic reticulum
  • Roughage
  • Round heart
  • Rovsings sign
  • Rubisco
  • Rudiments
  • Rudp carboxylase
  • Rue
  • Ruffle
  • Rummel tourniquet
  • Runner
  • Runt disease
  • Rushes
  • Rushton bodies
  • Rust
  • Home
  • Dictionary
  • Articles
  • Tutorials
  • About Us
  • Contact Us
  • Editorial Guidelines

The content on this website is for information only. It is not intended to provide medical, legal, or any other professional advice. Any information here should not be considered absolutely correct, complete, and up-to-date. Views expressed here do not necessarily reflect those of Biology Online, its staff, or its partners. Before using our website, please read our Privacy Policy.

© 2001-2025 BiologyOnline. All Rights Reserved