The Major aspects in Astrology
These aspects are commonly used and are most influential.

Conjunction ☌0° (0-6) or in the same sign

Energies blend, fusion, merging, can cause friction
Planting a seed or acting upon what you’ve planted
New beginning
Subconsciously driven
Transit : A feeling within you, you taking action most of the time
Considered harmonious depending on the planets involved
Could act as a blind spot especially with the Sun (=combust)
In aspect maximum orb of 6°
Associated with number 1
Sextile ⚹60° or 2 signs apart

Supporting, cooperation, opportunity, makes lazy
Needs more effort than the trine aspect
Activity, choice, integrate
Conscious
Transit : Good for harmonizing relationships
Considered harmonious but makes lazy, weakest aspect, shows possible talents
In aspect maximum orb of 3°
Associated with number 6
Square □90° or same modality

Friction, conflict, difficulty, instability, frustration
Getting things moving, change, powerful
Dynamic change, stimulate action, passion
Increase self-awareness, expression
Transit : Brings tension, action or breakups in relationships
Could be considered as ‘good’ because it stimulates action
Acts like Mars energy
In aspect maximum orb of 3°
Associated with number 4
Trine △120° or same element

Assist, opportunities, harmony, natural talents
Solutions, mediation, cooperation
Passive
Transit : Brings new opportunities in relationships, circumstances
Acts like Venusian energy
In aspect maximum orb of 5°
Associated with number 3
Opposition ☍180° or in the opposite sign

Attraction, separation, challenge, polarizing, confrontation
Things beyond your own control, cooperation
Objectivity vs subjectivity
Transit : Others or circumstances outside of your control create events
Different energies
Acts like Saturnian energy
In aspect maximum orb of 5°
Associated with number 2

The Minor aspects
These are not so common in practice but can give deeper insight onto the whole story of a horoscope.

Semi-Sextile 30° or the neighbor

Subtle friction, differences, awkward
Unrealized potential
Connector to other aspects involving one of the planets
Need to learn the differences and compromise
“You have what i don’t have”
Healing & transformation
Common in a natal chart, not so much in synastry
In aspect maximum orb of 3°
Associated with number 7
Bi-Quintile bQ144° or 6 signs apart

Creative power. Stimulate & use gifts
Inactive ability, vaguely aware
Mental & psychological energy
In aspect maximum orb of 3°
Quincunx ⚻150°

Differences, lack of common ground, intolerant
Stressful, discomfort, affects what it touches
Push-pull, Ping-pong, quick change
separate expressions, individual functioning
In aspect maximum orb of 3°
Associated with number 5