There are some verbs which are both ergative and reciprocal. Verbs of this kind have the label V-RECIP-ERG in the Collins Cobuild English Dictionary.

A typical ergative reciprocal verb has the following features:

1 Like an ergative verb, it has both patterns where the verb is not followed directly by a noun group (for example pl-n V and V with n) and patterns where the verb is followed directly by a noun group (for example V pl-n and V n with n). The person or thing indicated by the Subject of the first kind of pattern may also be indicated by the noun group following the verb in the second kind of pattern. For example: The oil mixes with the other ingredients; She mixed the oil with the other ingredients.

2 Like a reciprocal verb, it has a pattern where the verb is used with a plural Subject indicating the participants in an action (for example pl-n V), and one or more patterns where one participant is indicated by the Subject and the other is indicated by the Object, prepositional Object, or Adjunct (for example V with n). For example: The salt water and fresh water mix; The salt water mixes with the fresh water.

Ergative reciprocal verbs all indicate that two or more people, groups, or things join together or are linked in some way, or that someone or something causes two or more people, groups, or things to join together or be linked.

An ergative reciprocal verb has one of these three pattern combinations:

• Pattern combination 1: pl-n V; V with n; V pl-n; V n with n
  The liquids will blend to make a rich sauce. The chocolate blends with the coffee. Blend the remaining ingredients. Blend the butter with the sugar.

*Pattern combination 2: V; pl-n V n; V n with n
The peace talks will reopen tomorrow. The two groups reopened talks yesterday. They have reopened negotiations with the government.

*Pattern combination 3: pl-n V; V n; V pl-n; V n to/with n
The chairs all matched. Her hat matched her coat. Match the two lengths of cloth. We will match the fabric to your existing furnishing.

These verbs have four patterns. Two patterns are reciprocal:

Two patterns are not reciprocal:

Verbs with this combination of patterns belong to the following meaning groups:

In the patterns pl-n V and V with n, these verbs indicate that two or more things or people join together or touch. In the patterns V pl-n and V n with n, they are concerned with someone or something joining things or people, or making them touch.

In the patterns pl-n V and V with n, these verbs indicate that two or more things or people have a connection. In the patterns V pl-n and V n with n, they are concerned with someone or something connecting things or people.

• They are ideally suited to organisation-wide work-group computing, where all users are interconnected.

In the patterns pl-n V and V from n, these verbs indicate that two or more things or people move apart or stop being connected, physically or metaphorically. In the patterns V pl-n and V n from n, they are concerned with someone or something moving things or people apart or ending a connection between them.

In the patterns pl-n V and V with n, these verbs indicate that two or more things are similar or compatible in some way. In the patterns V pl-n and V n with n, they are concerned with someone or something using or putting two or more similar or compatible things together, or putting them together successfully.

We include here line up, which is concerned with putting two or more things in the right position relative to each other.

In the patterns pl-n V and V with n, these verbs indicate that two or more things occur or do something alternately or swap roles or places. In the patterns V pl-n and V n with n, they are concerned with someone or something using two or more things alternately or swapping them over.

These verbs have three patterns. Two patterns are reciprocal:

One pattern is not reciprocal:

Verbs with this combination of patterns belong to the following meaning groups:

These verbs indicate that two or more countries, groups, or people start communicating with each other again.

These verbs indicate that two or more people put their drinking glasses together or touch each other. They have the patterns pl-n V, pl-n V pl-n, and V pl-n with n.

These verbs have four patterns. Two patterns are reciprocal:

Two patterns are not reciprocal:

There are five verbs with this combination of patterns. The verbs match and overlap have the pattern V n with n. The verbs marry, match and touch have the pattern V n to n.

• We were wed in 1928 and had a very happy marriage.

When ergative reciprocal verbs are used in patterns with a plural Subject, they can be emphasized with phrases in the same way as ordinary reciprocal verbs (see Chapter 6). With most of them, a reciprocal pronoun (each other or one another) can be used after the appropriate preposition or after the verb.

• The third possibility is that building societies may merge with each other.
• These muscles overlap each other. With the verbs listed below, the adverb together can be used for emphasis.
• Given enough speed, nuclei fuse together and make a new, heavier element.
• Biological, psychological, and cultural factors all mesh together to produce illness.