Here is the Jain monastic hierarchy in simple terms, with the main differences between the two major traditions:

• Acharya

- The head of a monastic order. Responsible for guiding the order, preaching, and supervising teachings and ordinations.

• Upadhyaya (and Elacharya in some lineages)

- A senior, highly learned monk who teaches the scriptures and conducts important ordinations. In many lines of Śvetāmbara tradition, Upadhyaya is a key senior rank just below the Acharya. - In Digambara paths, Elacharya is a title used for a senior teacher who helps guide the order.

• Muni (Sadhu) / Sādhu

- A general monk who has taken the vows and follows the monastic code. The term “Muni” is commonly used in Digambara; Śvetāmbara mendicants may use “Sādhu.” - The Muni is typically under the guidance of the Acharya and Upadhyayas.

• Ailak (and Kshullak)

- These are junior ascetics in the Digambara tradition. Ailak uses one piece of cloth; Kshullak uses two pieces. They are trainees or younger ordinees within the monastic community.

• Brahmachari (Brahmacharini for nuns)

- A stage for younger or beginner monks and nuns who have begun rigorous practice but are not yet at the senior levels.

• Śrāvaka (Śrāvika for lay followers)

- This term is for householders who are on the path toward monkhood or who support the monastic order; not a monastic rank themselves but part of the broader Jain sangha.

Nuns (female monks) and the corresponding titles in Digambara and Śvetāmbara traditions:

• Digambara: Aryika Pramukha (senior), Aryika, Mataji, Kshullika, Brahmacharini
• Śvetāmbara/Terapanth (and some other Śvetāmbara groups): Sadhvi or Ganini Aryika (senior), Aryika, Mataji, Brahmacharini

Important note:

• The exact titles and order can vary by sect (Digambara vs Śvetāmbara) and by sub-traditions (for example, Terapanth has its own naming for junior monks). The core pattern, however, is a hierarchy led by an Acharya, supported by senior preceptors (Upadhyaya/Elacharya), with Muni/Sadhu below, and junior ordinees (Ailak/Kshullak) progressing toward higher roles as they study and practice.

If you’d like, I can point you to a page on JainKnowledge.com that describes monastic ranks in more detail.