observance (n.)
- accommodation
 - accord
 - accordance
 - acquiescence
 - adaptation
 - adaption
 - adherence
 - adjustment
 - adoration
 - advertence
 - advertency
 - agreement
 - alertness
 - allegiance
 - assiduity
 - assiduousness
 - attention
 - attentiveness
 - awareness
 - care
 - celebration
 - ceremonial
 - ceremony
 - cognizance
 - commemoration
 - commencement
 - completion
 - compliance
 - concentration
 - conformance
 - conformity
 - congruity
 - consciousness
 - consideration
 - consistency
 - consuetude
 - convention
 - conventionality
 - convocation
 - correspondence
 - cultism
 - custodianship
 - custody
 - custom
 - devotedness
 - devotion
 - devoutness
 - diligence
 - discharge
 - dutifulness
 - duty
 - ear
 - earnestness
 - effectuation
 - enforcement
 - espial
 - espionage
 - etiquette
 - examination
 - execution
 - exercise
 - exercises
 - faith
 - faithfulness
 - fanfare
 - fashion
 - fealty
 - festivity
 - flexibility
 - form
 - formal
 - formality
 - formula
 - formulary
 - fulfillment
 - function
 - graduation
 - guard
 - guardianship
 - habit
 - harmony
 - heed
 - heedfulness
 - holiday
 - homage
 - inaugural
 - inauguration
 - initiation
 - inspection
 - institution
 - intentness
 - invigilation
 - jubilee
 - keeping
 - line
 - liturgy
 - looking
 - lookout
 - loyalty
 - malleability
 - manner
 - manners
 - mark
 - memorialization
 - memory
 - mind
 - mindfulness
 - monitoring
 - mores
 - mummery
 - mystery
 - note
 - notice
 - obedience
 - observation
 - office
 - ordinance
 - orthodoxy
 - ovation
 - performance
 - pietism
 - piety
 - piousness
 - pliancy
 - practice
 - praxis
 - prescription
 - prosecution
 - prudence
 - recognition
 - reconciliation
 - regard
 - rejoicing
 - religion
 - religionism
 - religiousness
 - remark
 - remembrance
 - respect
 - revel
 - reverence
 - rite
 - ritual
 - rituality
 - sacrament
 - salute
 - salvo
 - scrutiny
 - service
 - servility
 - solemnity
 - solemnization
 - spying
 - stewardship
 - strictness
 - submission
 - submissiveness
 - surveillance
 - testimonial
 - theism
 - thought
 - toast
 - tradition
 - traditionalism
 - transaction
 - tribute
 - triumph
 - uniformity
 - usage
 - use
 - veneration
 - viewing
 - vigil
 - vigilance
 - wariness
 - watch
 - watchfulness
 - watching
 - way
 - willingness
 - wont
 - worship
 
But to my mind, though I am native here
And to the manner born, it is a custom
More honoured in the breach than the observance.
Suit the action to the word, the word to the action; with this special observance, that you o'erstep not the modesty of nature.