Plagiarism is not a similarity percentage

What you need to know

Similarity checking is usually described as if there were a single number: clear it and you graduate. Hence the question students ask in their first month — what percentage is allowed. The honest answer is unwelcome: the percentage is not the rule. The rule is attribution, and the offence is defined by it, not by a figure.

The difference becomes visible when three universities are compared. One has no threshold at all: using a source without a citation is in itself an attempted deception. Another has a threshold, and a high one. A third has a lower threshold that may be exceeded if the supervisor explains why. A single number that works everywhere simply does not exist.

How it works

1. Where there is no threshold. Technische Universität Berlin treats plagiarism as a serious breach of its examination regulations and describes it as an attempt to deceive: a source, including an online source, used verbatim or in modified form without proper citation; a text, graphic or image used without naming where it came from. No figure appears in that description.
2. Where there is a threshold. The University of Bologna checks final papers on a platform and publishes a maximum share of similarity against the reference database. Only those who fail the check are notified; for everyone else, silence means the check has been passed.
3. Where the threshold is lower but not final. At Babeș-Bolyai University the similarity report is endorsed by the thesis supervisor; if the share exceeds the threshold for a well-founded reason — the student's own article published before the report was generated, for instance — the supervisor must justify it in their own statement.
4. Which gives the main point. A similarity report is a tool for the supervisor and the board, not a permission slip for the student. It shows where to look; a person decides.
5. It is not only the thesis that is checked. The Berlin university states separately that this covers graded assignments and written or electronic examinations, with final theses handled under their own procedure. The rule therefore applies all year, not in the final week.

What counts as an offence

• Verbatim or modified use of a source without a citation, online sources included.
• A text, graphic or image without naming where it came from.
• Copying from another student — including on a task issued to you personally.
• Near-verbatim reuse of lecture material without naming its author.

What usually goes wrong

The threshold is read as permission. "Mine is lower, so I am fine" does not hold: a paper with zero similarity is still plagiarism if someone else's thought is presented as your own.

Paraphrase is taken for your own text. A reworded passage without a citation is the same case as a verbatim quotation without one.

People assume only the thesis is checked. Graded coursework and examinations are checked too.

People count on an appeal. The Berlin university warns outright that appeals are usually lengthy, costly and rarely successful.

The consequences beyond the grade are overlooked. There the examination counts as failed, the whole module has to be repeated, the case is reported to the examination office, and a repeat violation can lead to expulsion.

Where this is stated officially

• Technische Universität Berlin — plagiarism as a breach of examination regulations: what counts as attempted deception, how a case is handled, what follows.
• University of Bologna — checking of final papers: the platform, the maximum share of similarity, how students are notified.
• Babeș-Bolyai University — rules against plagiarism in bachelor's and master's theses: who endorses the report and when exceeding the threshold is acceptable.

How to find your own rule

Read the rules of your own faculty and your own programme rather than the university's general page: it is the faculty that sets the threshold and the procedure, and the neighbouring programme's will differ. Ask before your first written assignment, not before the defence: the rule applies from the first task.