改良 and 改革: improving qualities and reforming structures
Compare improvements to a machine or crop variety with changes to systems or organizations, focusing on the target rather than the scale alone.
Improving qualities with 改良
改良 (かいりょう) refers to improving the qualities of something. The example 「古い機械を改良して作業時間を短くした。」 is translated as “We improved the old machine and shortened the work time.” Improving the old machine shortens the work time. The sentence gives no numerical amount of time saved.
The example 「品種の改良によって寒さに強い作物が生まれた。」 is translated as “A cold-resistant crop was developed through varietal improvement.” Varietal improvement produces a cold-resistant crop. This property does not apply to every improved variety.
Reforming a system with 改革
改革 (かいかく) refers to reforming a system or organization. The example 「学校は入試制度の改革に向けて議論を始めた。」 is translated as “The school began discussions on reforming the entrance examination system.” The school begins discussions toward reforming the entrance examination system. Starting discussion does not establish completed reform.
The example 「古い組織を改革するには、現場の理解が欠かせない。」 is translated as “Understanding from staff in the field is essential to reform an outdated organization.” Reforming the outdated organization requires understanding from staff in the field. The requirement does not report that understanding has been obtained or reform completed.
Qualities and structures as targets
改良 emphasizes improving the qualities of a machine or variety; 改革 emphasizes reforming a system or organization. Minor versus major scale alone does not divide the words.
Separate shortened work time and the cold-resistant crop from the start of reform discussions and the understanding required for organizational reform. Discussion and requirements do not report completed reform.
What target matters more than scale when comparing 改良 of a machine or variety with 改革 of a system or organization?
Show the answer and why
For 改良, identify the qualities made better. For 改革, identify the system or organization being changed. Read the actual target, condition, and result rather than imposing a fixed minor-to-major sequence.